A system comprising: a low observable aircraft (2) having its external surfaces oriented at a limited number of directions; a device (12) mounted to the aircraft (2) outside the external surfaces of the aircraft (2); and a cover (10) located outside the external surfaces of the aircraft (2), the cover (10) being releasably coupled to the one or more external surfaces of the aircraft (2), at least part of the cover (10) being spaced apart from one or more of the external surfaces of the aircraft (2) so as to define a chamber between the cover (10) and that one or more external surfaces of the aircraft (2). The device (12) is wholly located within the chamber. One or more external surfaces of the cover (10) are oriented in the same direction as at least one external surface of the aircraft (2).
