Airlines canceling flights because the air is too hot

[The Velveteen Ocelot]

52. Long runways.

Planes can usually take off and land in high temperatures if the runway is long enough (though there are other issues, like brake overheating). The issue is density altitude - high temperatures have the same effect on the ability of an airplane to take off as high altitudes; in both cases the air is less dense so the engines are less effective and the less dense air flowing over the wings creates less lift. The longest runway at (hot) King Kahlid airport at Riyadh is almost 14,000 feet long, while the longest runway at (cold) KEF (Reykjavik, Iceland) is only 10,000' long - but both airports handle large, wide-body and military aircraft. El Alto in Bolivia, at a field elevation of over 13,000' msl, has a runway almost as long as King Khalid's, but because of the altitude, not the heat.