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”: