Hot air is less dense than cold air, meaning aircraft require more engine power to generate the same thrust and lift as they would in cooler climes. The conclusions are in part logistical and in part safety, as author and pilot Patrick Smith explains in his book, Cockpit Confidential.
“Hot air is less dense than cold, negatively affecting both lift and engine performance,” he writes. “The take-off roll will be longer and the climb shallower, and in very hot temperatures, a plane may no longer meet the safety margins for a particular runway – climb gradient parameters and the weight is determined for every take-off based on weather and runway length.
“Going a short distance with limited fuel is unlikely to be a problem, but full tanks or a heavy payload can put you up against the limits, and cargo or people will sometimes need to be bumped.”