Hot weather cancelling airline flights?

Dear Tom,
Recently, with the hot weather in the Southwest, many flights were canceled. I assume that it has to do with air density. Please explain why.
—Rod Vernon, Evanston
Dear Rod,
It certainly does. The density of air decreases as the temperature increases. As the air molecules move farther apart, the lift available for an airplane when it’s taking off decreases. Planes need more runway than is available and are unable to take off or land. The impact is greater on smaller jets that generate less thrust, and many regional jets have a temperature operating limit of 118 degrees. Southwestern U.S. temperatures generally do not get that high, so high-heat disruptions are infrequent. In notoriously hot areas like Dubai, United Arab Emirates, flights are clustered during the evening and early-morning, when temperatures are lower. Airlines also use larger planes.