Aircraft contrails consist mostly of water vapor, and evaporate in a matter of minutes, depending on air temp and relative humidity. The often mentioned chemtrails do not evaporate, instead they spread out into hazy cloud cover and last for hours. All one has to do is look up and observe. Commercial air traffic typically fly the same routes day after day. They don't fly crisscross tic tac toe patterns and repeatedly back and forth across the sky so that their trails blanket an area.
