Photo taken from the research aircraft Falcon of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt(DLR) at about flight level 33,300 feet of an Airbus A340 with contrails (left) and a Boeing 707 without contrails (right).
US Air Force employee in the course of their official duties
2005-10-13
<a rel="nofollow" class="external free" href="http://www.af.mil/shared/media/document/AFD-051013-001.pdf">http://www.af.mil/shared/media/document/AFD-051013-001.pdf</a>