September 03, 2001
On this morning photo taken in early August, a pair of jet contrails are seen paralleling each other over the skies of suburban Maryland. The older one is on the left and the younger one on the right. When contrails cross the sky, the atmosphere, at the level of the jet aircraft, has to be near saturation. On this morning, not only was the atmosphere above 25,000 feet sufficiently moist to allow the contrails to be visible over most of the sky, but light winds aloft kept them from rapidly dispersing.