Contrails, short for condensation trails, are the white streaks often seen behind airplanes flying at high altitudes. They form when hot, humid exhaust from aircraft engines mixes with the cold, low-pressure air of the upper atmosphere. This causes water vapor to condense and freeze into tiny ice crystals, creating visible trails. The persistence and appearance of contrails depend on atmospheric conditions like humidity and temperature; some disappear quickly, while others can spread and form ci