Is it Ever Too Cold to Fly?

Airliners are built for cold temperatures (it’s –57°C at cruising altitude) and aviators welcome the denser air that comes with extreme cold. Frigid air at –40°C is about one third more dense than hot air at +40°C. Cold air produces more lift over the wings and flight controls, and more thrust from the engines and propellers. Pilots say that an aircraft in cold air climbs “like a homesick angel.”

Extreme cold poses challenges on the ground, but we are Canadian cold experts. To start a jet engine requires oil temperatures above –40°C, so engines are preheated. Keeping machinery warm, promptly connecting warm cabin air, having hot–air heaters nearby and wearing extra layers of clothes are all part of doing business in the Canadian winter. Even when the mercury plummets, our goal remains to get you to your destination safely and expeditiously.

December 20, 2019
An illustration of a plane flying over mountains within a snow globe with a thermometer sticking out of it

Frigid Facts

  1. If an aircraft remains at the gate overnight, ground power must remain on to prevent the water lines from freezing, and if it’s parked off the gate with no power, the water is drained.

  2. Below –40°C, air no longer holds liquid moisture. We meteorologists call this homogeneous nucleation. Basically, the moisture freezes out of the air. It’s also the threshold where aircraft deice equipment is no longer required.

  3. High clouds, with bases starting above 20,000 feet, are composed entirely of ice crystals because of the frigid temperatures aloft.

Portrait of Air Canada's Captain Doug Morris
Photo: Reynard Li

Doug Morris is an author, meteorologist, instructor and Air Canada captain on the Boeing 787.