A gas turbine engine assembly includes a turbomachine including a compressor section, a combustion section, and a turbine section in serial flow order; a fuel delivery system operable with the combustion section of the turbomachine for providing fuel to the combustion section of the turbomachine; and an air cycle assembly including an air cycle machine and a heat exchanger, the air cycle machine in airflow communication with the compressor section of the turbomachine and the heat exchanger in airflow communication with the air cycle machine. The gas turbine engine assembly also includes a thermal transfer bus thermally coupling the heat exchanger of the air cycle assembly to the fuel delivery system for transferring heat from the air cycle machine to the fuel delivery system.