Hotter air may lead planes to carry fewer passengers

Air travel can be annoying. But research now suggests global warming could make it much worse. To get off the ground in really hot weather, planes may be forced to carry fewer passengers. That might mean a little more elbow room, which would be good. However, it also would make flying more expensive. 

Average air temperatures around the world are rising. That global warming is happening because people are polluting the air with increasing amounts of greenhouse gases. These gases, such as carbon dioxide, are a byproduct of burning fossil fuels. Their rising levels help to hold in energy from the sun, causing ground-level temperatures to rise.

Those warmer temps can affect an airplane’s ability to fly. That’s because air molecules spread out more as the air warms. This generates less lift under a plane’s wings as it barrels down a runway. To compensate, a plane must be lighter to take off in hot weather than on cooler days.

It can even prove too dangerous for some planes to attempt a take-off. A record June heat wave in the American Southwest, for instance, caused flight cancellations in Phoenix, Ariz. One airline’s planes were cleared to operate only up to 47.8° Celsius (118° Fahrenheit). On June 20, Phoenix reached a blistering 48.3 °C (119 °F)!

Radley Horton is a climate scientist at Columbia University in New York City. Two years ago, he and graduate student Ethan David Coffel projected the impact of warming at four U.S. airports. The trajectory of expected warming could triple the number of days when planes face weight restrictions, they calculated.

Horton and his colleagues have now expanded on those earlier projections. They probed the impact of rising temps on five types of commercial planes flying out of 19 of the world’s busiest airports. In the coming decades, as many as one to three out of every 10 flights that take off during the hottest time of day could face weight restrictions, they found. In some cases, a typical 160-seat plane would have to jettison 4 percent of its weight. That would be the equivalent of taking a dozen people off the plane, the researchers calculated.

Their study was published online July 13 in Climatic Change.