Furthermore, the Air Force performs missions during which, exhaust is released into the atmosphere. The exhaust emissions produced by aircraft and space launch vehicles can produce contrails that look very similar to clouds whcih can last for only a few seconds or as long as several hours. Vapor trails are formed only under certain atmospheric conditions and create a visible atmospheric wake similar to a boat propeller in water and usually dissipate very rapidly. Contrails consist ofice particles that form or nucleate around the small soot or aerosol particles in the exhaust hases. The contrails are formed when the relative humidity increases because of the mixing of warm and moist exhaust gas with colder and less humid ambient air of the atmosphere.
Contrails become visible roughly about a wingspan distance behind the aircraft.
Contrails can be formed by propeller or jet turbine powered aircraft. The contrails formed by the exhaust at high altitude are typically whicte and very similar to cirrus clouds. As the exhaust gases expand and mix with the atmosphere, the contrails diffuses and spreads. At sunsets, these contrails can be visibly eye-catching and striking as they reflect the blue, yellow and red spectrum of the reflected sunlight. A different type of contrail or condensation trail is caused when a wing surface or winglet causes a cavitation of iar in very humid conditions.