Stories
Unraveling the Mystery: Why Do Planes Leave White Trails in the Sky?
- •The long white trails behind planes, known as contrails, are not smoke or chemicals but condensation trails made of tiny ice crystals.
- •Contrails form when hot, moist engine exhaust meets extremely cold air at high altitudes (8,000 meters or higher, -50°C to -70°C).
- •The persistence of contrails depends on atmospheric humidity; dry air causes them to disappear quickly, while moist air allows them to linger for hours.
- •Higher altitudes increase the likelihood of contrail formation due to colder surrounding air.
- •Persistent contrails can spread into cirrus-like clouds, potentially having a small warming effect on the Earth's atmosphere.
Key Questions Answered
These white trails, known as contrails or condensation trails, are formed when the hot, moist exhaust from aircraft engines meets the freezing air at high altitudes (around 8,000 metres or higher), causing the water vapour to rapidly cool and freeze into tiny ice crystals.
The persistence of a contrail largely depends on atmospheric humidity. When the surrounding air is dry, the ice crystals quickly evaporate or sublimate, making the trail vanish soon after formation. However, if the upper atmosphere has high moisture levels, the ice crystals persist and can spread into long-lasting clouds.
Yes, persistent contrails can spread into thin, cirrus-like clouds that influence heat retention in the Earth's atmosphere, resulting in a small warming effect.
