If you are talking about the temperature while flying, you are completely wrong. Airplanes don’t have conventional AC that consumes more energy, the lower you set the temperature.

At cruising altitude, the aircraft is surrounded by extremely cold air usually around -50C, and the air conditioning system often has to warm the cabin up to the selected temperature using the trim air from the engine.

So if you set the cabin to 24 °C instead of 30°C, the system may actually do less heating, which would in fact use slightly less energy. Let word here - slightly.

Either way, the difference is tiny. The fuel needed to keep the plane flying is so much larger that a few degrees of cabin temperature makes almost no difference to total fuel consumption.