Contrails, short for "condensation trails," are streaks of cloud that form behind aircraft flying at high altitudes. They occur when hot, humid air from the aircraft's engines mixes with the colder air at high elevations, causing water vapor to condense and freeze into tiny ice crystals. These trails can vary in appearance and duration, depending on atmospheric conditions. The presence of contrails can influence weather patterns and climate. When they persist and spread out, they can form cirrus clouds, which may trap heat in the atmosphere. This interaction between contrails and the environment is an area of ongoing research in the field of climate science.