A method for operating an aircraft having two or more engines (10A, 10B), the method comprising: receiving a pilot-initiated request to operate the engines (10A, 10B) in an asymmetric operating regime; and commanding the engines (10A, 10B) to operate in the asymmetric operating regime in response to the pilot-initiated request, characterised in that the method further comprises: receiving an engine availability confirmation when a set of engine parameters meet engine operating conditions for the asymmetric operating regime, wherein a first of the engines (10A, 10B) is in an active mode to provide motive power to the aircraft and a second of the engines (10A, 10B) is receiving fuel and operating in a standby mode to provide substantially no motive power to the aircraft; receiving an aircraft availability confirmation when a set of aircraft parameters meet aircraft operating conditions for the asymmetric operating regime; and outputting an availability message to a cockpit of the aircraft in response to receiving the engine availability confirmation and the aircraft availability confirmation; and delivering fuel to both the first engine and the second engine when the first engine and the second engine are operating in the asymmetric operating regime. receiving a pilot-initiated request to operate the engines (10A, 10B) in an asymmetric operating regime; and commanding the engines (10A, 10B) to operate in the asymmetric operating regime in response to the pilot-initiated request, characterised in that the method further comprises: receiving an engine availability confirmation when a set of engine parameters meet engine operating conditions for the asymmetric operating regime, wherein a first of the engines (10A, 10B) is in an active mode to provide motive power to the aircraft and a second of the engines (10A, 10B) is receiving fuel and operating in a standby mode to provide substantially no motive power to the aircraft; receiving an aircraft availability confirmation when a set of aircraft parameters meet aircraft operating conditions for the asymmetric operating regime; and outputting an availability message to a cockpit of the aircraft in response to receiving the engine availability confirmation and the aircraft availability confirmation; and delivering fuel to both the first engine and the second engine when the first engine and the second engine are operating in the asymmetric operating regime. receiving an engine availability confirmation when a set of engine parameters meet engine operating conditions for the asymmetric operating regime, wherein a first of the engines (10A, 10B) is in an active mode to provide motive power to the aircraft and a second of the engines (10A, 10B) is receiving fuel and operating in a standby mode to provide substantially no motive power to the aircraft; receiving an aircraft availability confirmation when a set of aircraft parameters meet aircraft operating conditions for the asymmetric operating regime; and outputting an availability message to a cockpit of the aircraft in response to receiving the engine availability confirmation and the aircraft availability confirmation; and delivering fuel to both the first engine and the second engine when the first engine and the second engine are operating in the asymmetric operating regime.