Chemtrails are long and line-shaped cloud formations artificially created by flying air crafts which are NOT formed by condensation of water vapor in the aircraft's exhausts. While in fact the typical white trails left by traditional airplanes flying at high altitude last only a few minutes and are formed by condensation of water vapor in the aircraft's exhausts (contrails), chemtrails are supposedly filled with chemical substances employed specifically for supposed atmospheric and weather modification, biological testing or other classified purposes.