Other answers already address the engine performance loss and lift loss, but about that: > Doesn’t heat generate lift, like in gliders crossing hilly terrain?

Other answers already address the engine performance loss and lift loss, but about that: > Doesn’t heat generate lift, like in gliders crossing hilly terrain? That lift is generated by a temperature difference, not a globally high temperature. Thermals used by gliders are thermals because the air is locally hotter than the environment. If the whole environment gets warm, you don't get thermals.