A method is provided for operating a hybrid-electric propulsion system of an aircraft. The hybrid-electric propulsion system (100) includes a gas turbine engine (10) having a high pressure system, a low pressure system, an electric machine (102) coupled to at least one of the high pressure system or low pressure system, and an energy storage unit (104). The method includes operating the electric machine as an electric generator to charge the energy storage unit during a flight operation of the aircraft; switching the gas turbine engine to an electric operating mode during or after a landing operation of the aircraft; driving a system of the gas turbine engine using power from the energy storage unit while in the electric operating mode to provide or assist with providing ground operations the aircraft.