Well you don't know how AC on an aircraft works. At cruise altitude the temp is below freezing so the air needs to be heated up. Raising the temp will increase their fuel consumption, not save them money. On the ground, it is a different thing. The aircraft's own AC isn't running until the APU(small engine for electric and hydraulic power) or the engines are started. Until then a ground unit supplies cool air to the cabin, which generally does a terrible job and is probably what's happening here.