A method of operating an engine of an aircraft, the engine having a bleed air system. The method includes in flight, directing pressurized air from a source of pressurized air external to the engine to the bleed air system of the engine. An aircraft, comprising a first engine having a bleed air system, a second engine having a bleed air system, and a source of pressurized air that is external to the first and/or the second engine, the source of pressurized air being selectively fluidly connectable to the bleed air system of the first and/or the second engine, is also disclosed.