I've sat on many a commuter airplane in Texas in the late 70's and eary 80's sweating until after takeoff - it used to be considered "part of the territory" when flying from Texas in the summer on smaller commercial aircraft. Makes you wonder how people tolerated the weather "back in the day" before everyone got so soft.

Not having air conditioning is certainly an inconvenience, but it does not affect an airplane's abilty to operate safely. I'd rather get where I'm going than be delayed to fix an air conditioner.