After remote controlled tethered rig tests from 1947 to 1950 and a flying rig in 1951, Ryan was awarded an Air Force contract in 1953 to develop an actual flying jet-powered VTOL aircraft, which was given the designation X-13. It was only 24 ft long - just large enough to accommodate a cockpit (again with a tilted seat) and the 10,000 lb thrust Rolls-Royce Avon turbojet. Its high mounted delta wing had a wingspan of only 21 ft, capped with flat endplates. At the tip of the nose was a short pole ending in a hook. The hook was used to capture a wire on a vertical trailer bed. Once captured, the trailer was lowered to horizontal and could be transported on the ground. Engine thrust was vectored to provide pitch and yaw control in hover, while roll was provided by puffer jets outboard of the endplates. The first prototype was fitted with a temporary landing gear and made its first horizontal flight on 10 December 1955. It later made full conversions to vertical attitude and back at altitude. The landing gear was then replaced by a rear mounted castoring framework, known as the "roller-skate" and hooking practice was conducted. The second prototype followed a similar progression; on 11 April 1957, it made a vertical take-off from the raised trailer, transitioned to horizontal flight and back, ending with hooking on the wire "trapeze." On 28-29 July of that year, the X-13 was demonstrated in Washington, hovering across the river to the Pentagon. The Air Force chose not to continue development of the Vertijet because of the lack of an operational requirement.