Abstract: A method and apparatus are disclosed for a turboprop-powered medium altitude long endurance (MALE) aircraft, having: a heat exchanger with a heat-storage material, for example a heat-storage wax; and an air recirculation path. The heat exchanger can be arranged to cool air recirculating around the air recirculation path which is arranged to provide cooling to the MALE aircraft, for example to an equipment bay. The heat-storage material may be cooled by ground-based cooling apparatus when the aircraft is on the ground and/or by ram air when the aircraft is in flight. The heat-storage material may have a melting point selected so as to be rendered solid during ground-based cooling and/or ram air cooling, and/or selected so as to undergo melting whilst cooling the air recirculating around the air recirculation path.