A cover means for the navigational instruments and radio equipment of an aircraft that are mounted on and arranged for removal from the aft face of the instrument panel of such aircraft which cover means includes a cover provided with lock means that are arranged to coact with cooperating lock devices mounted on such aircraft instrument panel or other permanent structure of the aircraft so as to prevent removal of such cover from said panel and consequently access to the instruments and equipment mounted thereon and thereby preclude their unauthorized removal or theft.