A method of operating a supply aircraft for in-flight recharging comprises: transmitting a deploy command signal from a communication unit of the supply aircraft to a communication unit of a receiver aircraft, to cause a line and drogue to deploy from the receiver aircraft; controlling at least one of the supply aircraft and the drogue to engage the drogue with a first end of an electrical cable of the supply aircraft, a second end of the electrical cable being connected to the supply aircraft; and transmitting a return command signal from the communication unit of the supply aircraft to the communication unit of the receiver aircraft, to cause the line and drogue to return to the receiver aircraft with the first end of the electrical cable. The supply aircraft is located behind the receiver aircraft and the deploy command signal is for causing the line and drogue to deploy rearwardly of the receiver aircraft.