A gas turbine engine

A cooling system for a gas turbine engine (10). The system comprises a fuel air heat exchanger (78) comprising a fuel passage (80) in thermal contact with an engine cooling air passage (82). The system further comprises a fuel deoxygenator (72) located upstream of the fuel air heat exchanger (78) configured to deliver deoxygenated fuel to the fuel air heat exchanger fuel passage (80). The system includes a valve (84) configured to moderate engine cooling air flow to the engine cooling air passage (82).