To provide an air conditioning system for aircraft which can perform air conditioning without deteriorating engine performance when air conditioning in the air frame of the aircraft is performed.

The air conditioning system SYS for the aircraft to perform conditioning in the air frame of the aircraft using exhaust gas G1 discharged from an engine E is provided with a flow passage 1 which is provided between the engine E and the inside of the air frame and can flow the exhaust gas G1, a heat exchanger HE which is provided in the middle of the flow passage 1 and adjusts the exhaust gas G1 from the engine E to a prescribed temperature, and an ejector 2 which is provided in the middle of the flow passage 1 and introduces open air G2 to the flow passage 1 based on the pressure of the exhaust gas G1 passing through the flow passage 1 or the flow amount per unit hour.