Cirrus Uncinus and Contrails


I took these photos around 8AM this morning, Feb 4th 2009, in Los Angeles.




They show Cirrus Uncinus clouds, with a contrail running through them.

Cirrus uncinus clouds (or “Mares’ Tails”), according to wikipedia:

Cirrus uncinus is a type of cirrus cloud. The name cirrus uncinus is derived from Latin, meaning “curly hooks”. Also known as mares’ tails, these clouds are generally sparse in the sky, and very thin.

The clouds occur at very high altitudes, at a temperature of about minus 40-50 degrees Celsius. They are generally seen when a warm or occluded front is approaching. They are very high in the troposphere, and generally mean that precipitation, usually rain, is approaching.

And indeed, looking at the forcast, rain is coming, predicted for tomorrow and the next three days.

The long “tails” of the cirrus uncinus clouds are actually precipitation – very high snow in the form of tiny ice crystals falling through the air.  The wind blows these sideways, giving the distinctive hook shape.

The contrail in the same region is persisting for the same reason the clouds persist – it’s in a region of the atmosphere where there is moisture.  Notice the abrupt end of both the the contrail and the clouds at the left of the second photo. Contrails are a form of cirrus cloud, and if there is enough moisture in the air, a contrail will eventually spread to be indistingushable from the surrounding cirrus.  In this case though, the cirrus uncinus would have been exactly the same even if there were no contrails.

Twilight Zone Contrails

I was watching the first episode of The Twilight Zone, Where is Everybody, made in 1959, and I noticed that the movie poster had a nice depiction of some persistent contrails forming a grid:




I don’t think it’s a real poster, but it’s a real movie (Battle Hymn, with Rock Hudson), and a real 1959 episode of the Twilight Zone.  Just goes to show, contrails have been in American popular culture for quite a long time, at least fifty years.

If anyone recognizes the original image, please let me know where it’s from.

And while we are on the subject of posters, check this out:

http:[email protected]/433032511

Voodoo Contrails over Los Angeles

I was walking along this morning at around 10AM, when I noticed a huge semi circular contrail, somewhere to the south of LAX.  This is something I’ve never seen before.  The weather was very well suited for contrails, and there were quite a few criss-crossing the sky.

Then about half an hour later I saw another one.   Now it was really interesting.   I hurried home to get my camera, but by the time I was home things had blown east a bit, and I was not able to get a very good shot.

You’ll have to take my word for it – it was very impressive.   I’m hoping that people in the “chemtrail” community will also have seen it and will post some better photos, and I can update this post.

[UPDATE 12/4/08] Here’s one titled “A perfect circle”: 11/20/08 – “A Perfect circle in the morning”, taken by Bettina Gilois, Pacific Palisades, CA:

So what was it?   Well, I went to the FlightAware web site and looked for planes that looked suspicious.   I saw one flying over Catalina, with the call sign VooDoo1, so I looked at that, and bingo:


That’s the guy.  The text next to the plane reads:

291 377

Which means it’s a B722, flying at 29,100 feet, speed 377 knots, and it took off from LAX and is going to land there.   It’s still flying now, about three hours after I first saw it.

What is VOODOO1?  It’s actually a plane owned by Raytheon, N289MT, a test plane that they use to test avionics equipment:

Here’s the satellite photo for the region in the map, showing the high level wispy clouds, and some contrails.

The photo was taken around noon, by which time the plane was no longer leaving trails.  It’s quite possible it contributed to some of the haze over the the east.

UPDATE NOv 8th 2011 – It happened again.

This must be a somewhat regular occurrence. This time I was lucky enough to get a better shot, and to see the trails on the Aqua satellite image, which matches the first four circuits (one small in the south, and the others larger racetracks). The wind is obviously blowing from west to east.

People Don’t Notice Contrails

I find clouds fascinating.   If I see a lenticular cloud while driving I might nearly crash the car while straining for a better view.   I’ve only seen mammatus clouds once in my life, and stopped to try to take a photo.  I’m quite fascinated by contrails and contrail shadows, especially the “black beam” shadows that seem to extend in front of the contrail.   

Yet my fascination is not shared by the general population.  When I saw the mammatus there was nobody pointing up at the sky.    Other people on the freeway were not swerving their cars, despite the impressive black beam in front of them.   Why not?

Unfortunately, the answer is rather simple: they’re just not that into clouds.  

Yes, my cloud obsession is simply not shared by other people, much in the same way that I don’t understand my friends interests in certain sports, or cars, or the contestents on American Idol.   They might be similarly bemused by my lack of interest in such things.  But the point here is that most people’s interest in clouds is limited to A) is it sunny? and B) might it rain?

So it’s hardly surprising that the gradual increase in contrails over the last 30 years has gone much without comment.   Each year the sky looks pretty much the same as last year.    But then, you get some people who, for some reason, started looking at the sky with more interest, and they noticed, for the first time, that the sky sometimes gets covered by contrails that spread out into a layer of cloud.

They then sometimes slip down a slipperly illogical slope – if they had not noticed this before, then that means it was not there before, hence it just started, and hence again it must be something deliberate.   So the “chemtrail” theory is born – these persistent contrails are actually some kind of nefarious deliberate spraying by the powers that be.

You’ll note that this theory is based on one fact in the theorist’s mind: “I did not notice this before”.

So, if you did not notice something, and hence it did not exist until you noticed it, then what about all those people who have NOT yet noticed that contrails spread?  Do the contrails not spread for them?   

The reality is that the vast majority of people simply don’t pay much attention to clouds, or planes in the sky. The contrails have been there all their lives, and they might as well be noticing the type of covering used on the road outside their house, or what hairstyles the newsreaders have   For most people it’s stuff that is simply there, and does not impact their lives in one way or the other.  It changes slowly over time, but day to day you don’t notice any change.

Sometimes though some people notice things that others have not, and then you can get into an argument about how things are, or were.  One such argument took place in 1971 between celebrity activist Arthur Godfrey and Senator Gordon Allott, R-Colorado,  over possible effects of the then proposed supersonic transport (the SST, a high speed plane like the Concord).   

One of the concerns Godfrey raised about the SST was the possibility of excessive contrail coverage.  The problem of contrails creating clouds was well known in 1971, and Godfrey was well aware of this from personal experience.  But Senator Allott was simply a person who had never noticed these spreading contrails, and hence we get the following newspaper clipping from the March 11, 1971 Missouri Mexico Ledger: (See the 4th story across at the top: “Godfrey calls SST ‘Nonsense’“)

Godfrey tangled with Sen. Gordon Allott, R-Colo., when he said present jetliners are environment hazard enough without adding SSTs to the skies. Godfrey said he’d seen, on hunting trips to the Colorado Rocky Mountains, blue skies “clouded over” by jet contrails by 9:30 in the morning.

Allott said he’d lived in Colorado all his life without ever seeing jet contrails form clouds—and said he has too much respect for the environment go go on hunting trips and shoot animals.

If a US Senator failed to notice these spreading contails spreading in 1971, is it really that surprising that people still don’t notice them now?  Or that people who believe in “chemtrails” are simple people who have only now, for whatever reason, taken an interest in the skies.

Memphis Belle WWII Bomber Contrails – 1944

This is an excerpt from the 1944 film “The Memphis Belle: A Story of a Flying Fortress”. The full original film is public domain, and can be found here:…

The film shows contrail formation, including showing “broken” contrails.

Make sure you listent to the audio, as it explains how high the planes are, how cold it is, and why contrails form.

Here’s some similar footage:

Fighter and Bomber Contails, 1940s

Contrails are a common sight now, but prior the the advent of commercial jet travel in the late 50s, there was little reason for planes to fly high enough to form contrails.  However, during the Second World War, high altitude airial dogfights over the UK were quite common.  Contrails in the clear blue sky were a common part of wartime Britain.

This excerpt from a Pathe newsreel shows this quite clearly.   It’s a piece about a nice little english village called Meopham – which is in Kent, between London and the bombers.   The shots of the contrails are between pretty pastoral scenes, and puppies playing with kittens.

(Click on “Watch in high quality” on the Youtube version)

There are two shots of the same contrails. Interesting because you can see that the trails have persisted and drifted to the right. Judging by the amount of change, probably over 20 minutes. You can also see a new contrail being formed.

These contrails look a bit odd, fragmented. We are used to seeing contrails that are long and straight. But the contrails in the film were formed by actual fighter planes, where the pilots were trying to kill each other. Hence they would be climbing and diving, twisting and turning in an attempt to out-maneuver each other. The contrails would start and stop as they climbed in and out of contrail altitude.

While these few contrails are interesting enough, it was just a skirmish on the way to where the real action was taking place:  London, where the dogfights must have been incredible, leaving a criss-crossing web of trails:

The above photos show dogfights during the Battle of Britain in 1940.  The German bombers were accompanied by fighter planes which would try to defend the bombers from the British fighters.   They were at a high altitude to avoid anti-aircraft fire.  Hence you get these amazing patterns of contrails which tell a tale of life and death at 28,000 feet above London.

The British won the Battle of Britain by 1941, establishing control of the airspace, moving the battle to Europe.  This did not end the contrails, but brought a certain order to them.   Bombers departing for Europe would climb to cruising altitude before crossing the channel, and this created another kind of story in the sky:

The above photo shows St Paul’s Catherdral in London, with departing bomber contrails behind it.  This is probably the best photo of a persistent WWII contrail, showing the trail spreading and dropping “mares tails”, exactly like modern contrails sometimes do.  It’s such a good photo you might think it’s a fake, but the original came from the Hulton-Deutsch Collection and can be found in the Corbis photo library as part a retrospective titled “V-1 “Buzz Bombs“.

Here’s another book with contrail photos from 1945:

(High definition version here)

Here’s some American newsreel footage of contrails at the Battle of the Bulge, 1945:

Aerodynamic and Rainbow Contrails

You occasionally see very pretty photos of contrails, like this one:

Very pretty.  But what is it?  It’s clearly not a regular exhaust contrail, as the trail seems to start actually ON the wing, and it has a weird rainbow effect you don’t often find in exhaust contrails.

It’s actually an aerodynamic contrail.  It’s formed by the reduction of pressure in the air as it moves over the wing.  When the pressure of a gas falls, then its temperature also falls (the same principle as is used by your refrigerator).  The reduced temperature cause small drops of water to condense, which then may freeze.  The (frozen) drops get larger as more water condenses on them.  The different sized drops (or ice crystals) have different optical properties, which affect different wavelengths of light, which accounts for the “rainbow” effect.

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Clouds before Planes – Cloud Studies 1905

The book “Cloud Studies” was published in 1905, over a hundred years ago.  It was written by Arthur W. Clayden, M.A., Former principal of University College, Exeter, UK. The book is available in PDF form since it’s out of copyright:

But the images are rather low quality, so I scanned them in from my copy of the 1925 edition (mostly the same photos), and I present them here:

It’s interesting that there are some clouds there that you might think look unnatural, or man made.  But these photos were taken before powered flight was invented.

So if you are ever looking up at the sky, and you see a cloud that looks a little odd, and you are wondering if this is a recent phenomenon, then have a look back at what clouds were like in 1905.  You’ll probably find your cloud here.

[Update March 23, 2011] I’ve also scanned in a good copy of the chapter on calculating cloud altitude using two cameras and the sun. This technique could easily (once the equations are worked out) be used to calculate the height of contrails, so would be highly recommended if you somehow suspect there’s some low-altitude spraying going on.


[Update Dec 12th, 2011]

High res scans of the 1905 version available on (in the HTTP section, the jp2 zip) The “read online” version is also very good.

Some of the photos were used in the earlier book CloudLand by William Clement Ley, 1894

WWII Contrails

There are lots of photos of contrails from World War II. I’ve collected a few of them here:

The collection shows all types of contrail formation – from the very short ones, to long persistent trails that spread out like cloud cover.

Why so many photos of contrails in WWII, and not so many from the 50’s and 60’s?  The simple reason is that contrails only form at very low temperatures, which are normally found at high altitude, and in peacetime there was NO REASON TO FLY THAT HIGH until the advent of commercial jet travel a few decades later.

The only reason these planes are flying that high is so they can avoid anti-aircraft fire.  The bombers fly as high as they can, and then their fighter escorts fly even higher, so they can see incoming aircraft targeting the bombers, and swoop down to attack.  This type of escorting is called “Top Cover”.  The most classic example of this is the famous photo “Top cover over J-Group”:

This photo was also taken over Emden, on September 27th, 1943, by Stanley M. Smith.
This photo was taken over Emden, Germany, on September 27th, 1943, by Stanley M. Smith.

Britain From Above – Air Traffic

There’s a great new series on the BBC in the UK: Britain From Above, that shows how various things look from a high perspective, using very interesting visualization techniques.

One of the most interesting (for me) was an episode that showed all the air traffic in UK airspace in a 24 hour period. That involved mapping the positions of 7,500 aircraft, showing how they crisscross the UK:

Here’s a video:

Here’s the same video on Youtube, if you can’t see the above:

This is just part of them, captured midway through the day.  But it’s interesting to see the width of the paths they fly along – particulalrly those that fly over London to Manchester and Scotland.   It’s also very interesting to see the area where paths cross.  These would very obviously give rise to the to contrail “grids” that some people feel are so suspicious.

Britain has nothing like the amount of traffic that the US has. According to the National Air Traffic Controllers Association:

On any given day, more than 87,000 flights are in the skies in the United States. Only one-third are commercial carriers, like American, United or Southwest. On an average day, air traffic controllers handle 28,537 commercial flights (major and regional airlines), 27,178 general aviation flights (private planes), 24,548 air taxi flights (planes for hire), 5,260 military flights and 2,148 air cargo flights (Federal Express, UPS, etc.). At any given moment, roughly 5,000 planes are in the skies above the United States. In one year, controllers handle an average of 64 million takeoffs and landings.

Here you can make out the shape of the US purely from the flight paths.  You can see the major cities, and the air links between them.  You can also see that there is really nowhere in the US where you don’t have commercial flights flying over you.  Even more, there’s hardly anywhere where you don’t have two or more flight routes intersecting near you.

For an interactive look at this data, see:

Interactive Flight/Contrail Map Visualization

So it’s no surprise that in regions where the weather is right for contrails to persist, then you’ll see some kind of “grid”, or intersecting contrails in the sky, like this:

Things That Are NOT Contrails (or Chemtrails)

Contrails are long thin clouds of ice crystals that form behind planes that fly through freezing cold air. Usually you see them behind jets at around 30,000 feet.  If the air they fly though has enough moisture in it already, then these contrail clouds can last for a long time before they evaporate.  Sometimes you get a lot of them at once in the sky, if the weather is right. They look like this:

Note: the trails in the above photo ARE CONTRAILS (and some natural clouds).  That’s a photo taken by NASA scientist Louis Nguyen from I-95 in northern Virginia, January 26, 2001.    This is the only photo of contrails in this article.  The remaining photos are NOT contrails.

There are several things that a superficially somewhat similar, in that they involve stuff coming out of the back of an airplane and/or lines in the sky.  But these things are not contrails.


Skywriting is making patterns in the sky using smoke trails.  Done at a low altitude using small planes, it can look very like a contrail, but it’s very different as skywriting is made from smoke (made from injecting oil into the hot exhaust), and contrails are made from ice crystals.


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Chemtrail Non-science

I’m very interested in contrails, but when you look for information about them on the internet, half the sites that turn up are about a conspiracy theory which claims that any trail that last more than a few minutes is actually a “chemtrail”, comprised of dangerous chemicals, particularly barium.

There are even web sites, where people who are convinced this theory is correct are taking the highly laudable step of attempting to verify their hypotheses with scientific experiments.

Unfortunately, they get the science terribly and inexcusably wrong. Take, for example, this graph found on the Arizona Skywatch site:

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Thirty Contrails, Forty Years Ago

This photo has the largest number of contrails I’ve seen in a single photo:


There seem to be at least 30, possibly more (click the photo for a larger verision).  What is even more remarkable is that it was taken sometime before 1967.  That’s over forty years ago.

The photo is plate 113 of the book Cloud Studies in Colour, by Richard Scorer and Harry Wexler, published in 1967 by Pergamon Press.  The photo was taken by Richard Scorer, probably in England.  The accompanying text reads:

Condensation trails are left by aircraft when the air is sufficiently cold for the mixture of air and exhaust to be saturated.  This does not usually happen except when the temperature is close to or below -40C, in which case the cloud freezes almost instantaneously and does not readily evaporate.  The cloud is then spread out by any wind sheer which may be present.

Germans Admit They Used Düppel!

Another bit of “Chemtrail” mythology was born with this YouTube video:


This video has been seized upon by the Chemtrail community as evidence that “chemtrails” are real, and that the German government has admitted they are spraying “chemtrails”.

Unfortunately the entire video is a very bad translation of a story about one Meterologist, Karsten Brand, who is was concerned that the military was using too much chaff (material used to disrupt radar). The military admitted that they do use chaff, but not too much, and it’s not harmful. Brandt contended they use so much it can affect the weather, and might be harmful to people. He’s also annoyed because it interferes with his weather radar.

There are numerous deliberate mistranslations, as pointed out in other places:

The German sentence which appears on screen is :

“Die Aufzeichnungen belegen, dass dabei sehr geringe Mengen von Düppeln ausgebracht werden”

The english sentence thats blended out at the same time reads :

“The registers report emissions of chemtrails at low altitudes”

(Note that you never see the full version of both sentences at the same time. One is wiped out as the other is filled in)

The actual translation should be more like :

“The reports show that very small quantities of chaff were used”.


The Meterologist behind all this, Karsen Brandt (show above, supposedly blaming it on “chemtrails”), actually goes out of his way to distinguish these odd cloud images from “chemtrails”, in this article, translated,

Following the publication of pictures of non-existent clouds on the radar we have been asked many questions. Here are the answers to the most frequently asked questions:

Are they “Chem Trails?
On various Internet sites there passionate arguments about aircraft spraying chemicals to either change the ozone hole or, acting for the United States (who else also ..), to change the weather – for world domination.  This is – according to the supporters of this conspiracy theory – not just an occasional trial, but regular, worldwide and especially in Germany. The sprayed chemicals leave greyish-white trails in the sky that are not like normal contrail, “Chem Trails” look quite different and also behave differently.

The beauty of this conspiracy theory is this: Everyone can see the trails, everyone may feel threatened, but no (normal) citizens can touch or examine them. The web pages show photos of various trails, and the “strange” pattern they leave behind in the sky.
For the layman, it is, at first glance, odd that one day contrails stay in the sky for hours, but the next day they dissolve within minutes .  However,  this “phenomenon” varies with the humidity and the change is very easy and simple to explain.
Of course, we also can not be absolutely excluded the possibility that a plane sprayed chemicals in the atmosphere.  But as regularly and as extensively as has been claimed by the conspiracy theorists, you can just use common sense to exclude.  For such a comprehensive worldwide conspiracy, there would have to be not only thousands of US pilots involved, but also scientists, German authorities, etc., etc. . How probably is it that with such a number of people, there is no leak?

The big problem with the video is the translation. In the shot above, the german word “duppel” is translated as “chemical trails (chemtrails)”, when the actual translation is “chaff”. The German word for “chemtrail” is “chemtrail“.

Another rather obvious distinction is that Brandt is talking about invisible clouds, whereas “chemtrails” are very visible (since they are aircraft contrails).

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How Long do Contrails Last?

Q) How long do contrails last?
A) According to all the books on clouds in the last 70 years, contrails last anywhere from less than a second, up to several hours. If depends on the atmospheric conditions at the altitude the plane is flying. It’s unrelated to the weather on the ground.

This is an oft-asked question. The answer is reasonably straightforward, but misunderstanding is common. To understand why a contrail can last as little as a fraction of a second, or as long as several hours, you need to understand what a contrail is, and how it forms.

Here’s another question, which has the same answer:

snowflakecvr2.jpgQ) How long does a snowflake last?

Why is this basically the same question? Because contrails are generally made of ice crystals. Jet exhaust contains a lot of water vapor (the chemical reaction actually produces more water than there was originally jet fuel), and when this gets shot out of the back of the engine at 2000MPH, it hits the frigid air (typically colder than -40 degrees), and the water vapor condenses and freezes, very quickly, into tiny ice crystals, just like snowflakes.

So why do these ice crystals sometimes stay around for a long time, and sometimes vanish in seconds? The temperature is well below freezing, so they can’t melt, can they? This is puzzling, because it involves something that most people know nothing about: “sublimation“.

Sublimation is when a substance (in this case, water), goes directly from being solid to being vapor (a gas), without actually melting into a liquid. It’s like evaporation, except instead of a liquid evaporating, it’s a solid (ice). If the air is dry (i.e. there is little water vapor in it), then the ice crystals will quickly sublimate into vapor, and the trail will vanish quickly.

However, if the air already has a lot of water vapor in it, then the ice will sublimate slower, and the trail will last longer.

If the air has so much water vapor in it already that it can’t hold any more (i.e. it’s “supersaturated”), then the ice crystals can’t sublimate, and so the contrail will stay around for a long time. The ice crystals might even attract water from the air, if there is enough, and the contrail will get thicker. Winds might make the contrail spread out to even cover the whole sky.

The above is a simplification, as other factors like temperature, pressure, and sunlight have an effect. But it explains the basic reasons why some trails last only a few seconds, and some can last for hours, and spread out to cover the sky.

Finally, there is one more way of asking the question:

Q) How long do clouds last?

This is the same question because contrails are clouds. Contrails are physically very similar to cirrus clouds (except they are long and thin), and so they act almost exactly the same. You see cirrus clouds that last for hours, so why not contrails?

References – note the dates

“A Color Guide to clouds” from Richard Scorer & Harry Wexler, 1963

1972: Richard Scorer – “Cloud of the worlds”



Contrails Above and Below

I took this photo on December 16, 2007, at around noon. It’s facing south from Los Angeles, California.


It was a particularly good day for contrails. You can see about seven in this photo. There’s also a nice contrail shadow, and a halo around the sun.

I was looking at the MODIS archive of satellite photos, and realized they had one for that date, and rather luckily it seems to have been taken within an hour of the photo I took, so it shows the exact same contrails from space. LA is just a bit to the right of the center of this photo.


As the photos are about an hour apart, the trails have shifted and distorted a little. But you can still match them up. Here I’ve color coded them.



It’s interesting also to look at the full size satellite photo of the area, so you can see where trails form, and where they do not form.


Los Angeles is in the middle of the photo. You can see the trails forming over Los Angeles, and it’s quite clear from looking the the cloud bands that they are forming in an area of high humidity.

Lookin up the coast, there is a gap in the clouds, and a corresponding lack of contrails. Then in the top left corner the clouds resume, and so do the contrails. In fact you can see several much thinner trails there. Here’s a close up:


These are probably the same planes that created the trails over Los Angles, just about an hour later, as they continue to fly north. The abrupt start of the trail as it enters the moist air is very obvious here.

This is all interesting in the context of the “chemtrail” theory. You often hear the chemtrailers posting things like “heavy spraying over Los Angeles today!!!” Then there are days with “no spraying”. MODIS is a wonderful resource for explaining why this perception happens. Sometimes there is a moist region of air at the right level over a particular place, and that place gets a lot of persistent contrails.

Looking at contrails from the ground only gives you a little bit of the picture. The satellite photos tell the whole story.

For example, here’s a “Massive Chemtrail Assault” Youtube video, from Austin, TX, 11/15/07

And here is the satellite image of the greater area from that day. Austin is on the right, towards the end of the huge sweep of clouds. It’s clear that the contrails are just forming around the edges of a region of high humidity.

Full Size original images here, about 1MB each:
My Photo: img_3175a.jpg
MODIS photo: aeronet_la_jolla2007350terra250m.jpg

Some more WWII Contrails

Here’s a newly discovered photo of contrail in WWII, this was taken by William Anderson, and uploaded by a grandchild of his, here. ( Creative Commons, Some rights reserved)



Update: The photo album has been updated with a much better scan:


You can see it’s taken from a photo album. I cropped, sharpened, and contrasted it a bit to bring out the details of the contrails. The text “Note Little Friends” probably refers to the fighter escorts making curved contrail in the background.

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Racetrack Contrails

Here’s a contrail you don’t see every day: the racetrack contrail (or, as I like to call this one, the paperclip contrail)


This photo was taken near Portland, Oregon on December 11th, 2005, at around 11AM.

So why would a plane be flying in this unusual pattern? Well, it turns out it’s not really very unusual. It’s called a “holding pattern“, and it’s a very specific pattern that planes fly in when they need to hold their position. Holding patterns have this very distinctive shape because the aircraft have to fly them in a very particular way that takes exactly four minutes to complete, so the ATC can know where they are, and when they will be facing in a particular direction. They fly straight for a minute, then turn 180 degrees over a minute, and then fly straight again. It looks like this:


For passenger jets, holding patterns are most common on the approach to busy airports (the one above is for Martha’s Vineyard), and it’s not too uncommon to make a few turns in a holding pattern shortly before landing. The contrails in the above photo is probably not this, as it’s at too high an altitude. Passenger jets do sometimes enter high altitude holdings (I’ve been in one once as a passenger), which could account for this.

poster360.jpgHigh altitude holds are also used by refueling tankers, as they wait for the planes they are going to refuel. Pilots obviously also have to train to fly in high altitude holds, and given the number of turns above, that’s the most likely explanation for this particular photo.

Remember the winds at altitude are typical around 50-100mph, so after the four minutes loop, the previous contrail could be blown around five miles away, giving the illusion that the plane is now holding over a different area. It’s not. The plane is playing over the same area, but the contrails have moved.

Of course, if you don’t know this, it might look a bit odd to you. Some people work these racetrack contrails into the “chemtrails” conspiracy theory. Look at this poster on the right. There’s a photo of a racetrack contrail with five turns, separated and distorted by the wind. Overlaid is the text “Look up, Phone Radio DJs”.

These racetrack contrails are pretty rare (unless you live near a training area), but hopefully now if you see one, you’ll be able to tell what is going on, and not feel the urge to call a DJ.

[BTW, the plane in the upper right of the poster is a Boeing E-6 Tacamo, dumping fuel]

[Update Oct 2011] This video shows one situation that can lead to racetrack contrails. If an airport, even hundred of miles away, is experiencing delays, then the incoming traffic might get put into a holding pattern.

Pre WWII Contrails

The Wright Brother’s first achieved powered flight in 1903. They only got a few feet off the ground, so of course did not leave a contrail. However it was barely more than a decade before planes inched into colder air, and the first reports began.

The earliest known account of a contrail is a passing mention attributed to Ettenreich, who in 1919 reported of an incident from 1915 where he saw “the condensation of a cumulus stripe from the exhaust gases of an aircraft”

In a fascinating article: Wakes of war: contrails and the rise of air power, 1918-1945 Part I–early sightings and preliminary explanations, 1918-1938, (Air Power History. 54.2 (Summer 2007): 16(16).), Donald R. Baucom give an account of the rise of high altitude flight, and the inevitable accounts of contrails, both persistent and otherwise, that occurred during that time. In the autumn of 1918, in an account of Captain Ward S. Wells, Army Medical Corps, who was serving with the 60th Infantry, 5th Division, American Expeditionary Force, during the Meuse-Argonne campaign.

Our attention was first drawn to the sky by the sudden appearance of several strange and startling clouds–long, graceful, looping ribbons of white. These were tapering to a point at one end and at the other where they dissolved into nothingness 60 degrees across the sky, were about as broad as the width of a finger held arm’s distance from the eye. On close observation we noticed some distance ahead of each cloud point the tiny speck of a chasse [sic] plane…. [N]ever before had I seen a plane writing in white upon the blue slate of sky.

This is very interesting, as it’s the earliest known account of contrails (note that these are non-persistent). It was also very novel and interesting at the time, and was reported in a letter to Scientific American, (“Clouds formed by Airplanes“, Jun 7, 1919, p 60) by Wells’ brother, Everett Wells, and provoked some discussion of what might be forming these clouds.

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