To be clear, 2°C is not going to significantly affect lift. Planes won’t to falling put of the sky on sunny days. Rather, airports and weight limits were designed around historic temperature maximums, and much higher maximum temperatures are showing up much more commonly. Adjusting these limits isn’t hard, but airlines are going to cry every step of the way and pass the cost ditectly to passengers.

Increased turbulence and higher winds are also a concern, increasing maintenance costs and travel times, as well as extreme weather shutting down airports more often.