We know that this summer in Euskal Herria has been very hot. But this has not happened only here. At Phoenix Airport in Arizona, for example, planes could not take off, since the temperature was higher than 50ºC. According to a spokesperson, older Boeing 727 and 737 and DC 9 aircraft had to stay on the ground until the temperature decreased below 50.
By decreasing air density with heat, it can be dangerous to take off for certain aircraft. Therefore, the new plans of the airlines try to deal with this problem.