“2. I have seen many planes turn the trails off and on thus the “naturally occurring” part goes out the window. Look up at the sky and chances are you will see the planes do it too or at the very least see trails that have gaps in them…”

Is cloud cover always continuous? Aren’t there often gaps between one cloud and the next?

“3. Ask your self why one day you see them “chemtrails” and then another day you don’t, did the airports shut down for a day?”

Ask yourself why sometimes you can see the stars at night and sometimes you can’t. Atmospheric conditions vary. Read a little bit about what contrails actually are (plenty of explanations on this very site), and the answer becomes crystal (snerk) clear. Also, if a plane doesn’t leave any kind of trail, that doesn’t mean it’s not there, but it does mean it might be very difficult for you to see with the naked eye.

There’s an interesting series of similar images here:

http://news.bbc.co.uk/2/hi/science/nature/8309629.stm

http://picasaweb.google.com/Uncinus/CloudsOfTheWorld1972?feat=embedwebsite#

Note particularly 11.2.3 which came from a single engine fighter jet. The photo was probably taken sometime in the 1960s. Not quite Donuts on a Rope, but then neither are many of the youtube videos.

http://picasaweb.google.com/Uncinus/CloudsOfTheWorld1972?feat=embedwebsite#5363663222513766242

I’d love to see a contrail from a Pulse Detonation Engine, but I suspect many of the candidates are just the result of normal factors. Have a look at this analysis:

http://chriswjohnson.blogspot.com/2007/01/donuts-on-rope.html

The aurora is documented for leaving odd trails – something to do with the way its engine works – in “pulses” so you end up with rings . . . it travels upward of mach 11 / 12 so “seeing” one is no mean feat since its usually long gone by the time you hear it :S

There is another trail reported to be from the same plane
http://www.nationalufocenter.com/images/aurora1.jpg

I have seen odd contrails – i believe they were from the aurora hypersonic jet and its pulse engine – “donuts on a rope”.

I’m not sure hypersonic speeds and pulse jets are necessary to produce this effect.
More likely a combination of span and wing loading.
Uncinus, what do you think?
Meanwhile, a couple of clips which seem helpful to me…

http://www.youtube.com/watch?v=XJk8ijAUCiI

http://www.youtube.com/watch?v=vU6M5hAe-TU

http://en.wikipedia.org/wiki/Morning_Glory_cloud

Clearly the video poster knew this, and was just trolling.