A control system for an aircraft hybrid propulsion system comprising a gas turbine engine coupled to an electric generator, a propulsor coupled to an electric motor, and an electrical storage device coupled to the motor and the generator. The control system configured to operate the propulsion system in a first descent mode and a second descent mode. In the first descent mode, the gas turbine engine is operated at a first engine power level and the generator is operated at a first generator power level. In the second descent mode, the gas turbine engine is operated at a second engine power level, higher than the first engine power level, and the generator is operated at a second generator power level, higher than the first generator power level. Electric power generated by the electric generator during operation in the second descent mode is stored in the electrical storage device.