Why Do White Trails Appear Behind Airplanes? Scientists Explain the Phenomenon

ISLAMABAD — Many people often notice long white streaks in the sky when an airplane passes overhead and wonder how they form. According to experts, these lines are called *contrails* (short for “condensation trails”).

Contrails are actually water vapor produced when fuel burns inside an aircraft’s engine. At high altitudes, where airplanes typically fly, temperatures can drop to nearly –55°C. In such extreme cold, the water vapor released from the engine quickly freezes into tiny ice crystals, creating the white streaks visible in the sky.

Experts say that when the atmosphere contains higher levels of moisture, these white trails remain in the sky for a longer period and stay clearly visible long after the aircraft has passed.

Interestingly, these trails sometimes appear not just white but also pink, orange, or golden. This happens due to the angle of sunlight, which reflects off the ice crystals and produces different colors.

Scientists also note that contrails are useful in weather and climate studies, as they help researchers assess atmospheric humidity, wind patterns, and changes in climate conditions.