A Contrail or vapour trails known to be line-shaped clouds produced by aircraft engine exhaust or changes in air pressure seen here in Singapore this evening. This is evident from aircraft cruising altitudes several miles above the Earth's surface. They are believed to be composed primarily of water, in the form of ice crystals. The combination of water vapor in aircraft engine exhaust and the low ambient temperatures that exist at high altitudes allows the formation of the trails. The jet looks like an Airbus A350 belonging to Malaysian Airlines.