It isn't uncommon for temperatures in Phoenix to be over 100°F in the summer. Is it true, though, that when the air temperatures get up over 115°F that Sky Harbor Airport cancels flights?
If you search around the Internet you'll see some interesting comments about this issue. I read where someone mentioned that when it gets to 140°F they cancel the flights. That might be true on the planet she was on at the time, but it has never been tested in Phoenix!
On June 26, 1990 Phoenix set an all time record high temperature of 122°F. I remember the day (although I didn't buy one of those tee shirts that said I survived it). Airlines stopped taking off and landing for part of the day, because at the time they did not have aircraft performance charts for a temperature that high. After that occurrence they received updated information, and resumed takeoffs and landings. If Phoenix was to post a temperature of 122°F now, takeoffs and landings would not be stopped by Sky Harbor International Airport because the charts have been updated.
As temperature increases, and humidity increases, the air becomes less dense, and therefore the air creates less lift for the airplane. It follows, then, that airplanes need more runway to take off. In 2000, the north runway at Sky Harbor International Airport, the longest, was lengthened to 11,490 feet long.
Each airplane has its own specifications that dictate, based on weight, engine performance, temperature, humidity, and elevation how much runway a pilot requires to safely take off. Sometimes air carriers will reduce their cargo loads on very hot summer days. It's rare that they would reduce the number of passengers; reducing cargo would make a bigger difference in weight.
Could a flight be postponed or canceled due to high temperatures in Phoenix? There are very few occasions where the temperature at the time of takeoff of any of our commercial flights at Sky Harbor International Airport creates a dangerous situation. Airlines certainly have the right to have more stringent requirements than the FAA does. An airline can choose to postpone or cancel a flight at any time. In the case of Phoenix summer temperatures, it's more likely that the flight might be postponed for a little while, so that passengers and/or cargo are not left behind.
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