Now more than 60 years since the type’s first flight in February 1954, and more than a decade after the very last examples were retired by the Italian Air Force, the F-104 still looks every inch the modern cutting-edge jet fighter. This view shows the mid-mounted trapezoidal wing and T-tail which was to be scaled up for the CL-400-10.

The first member of the Blackbird family unveiled to the public was the number 1 YF-12A, 60-6934. This photograph, taken at Groom Lake, shows the aircraft wearing a black anti-radiation paint mask and carrying two engine nacelle-mounted camera pods for AIM-47A missile launch test work.
Resembling a spaceship from the pages of the wildest contemporary science-fiction, the Lockheed YF-12 high-speed high-altitude reconnaissance aircraft was developed from the Archangel series of designs, the first step on the road to the world-beating SR-71 Blackbird.

Стратегический самолет-разведчик RB-57D-0 выполняет полет в сопровождении B-57B
In total 20 Martin RB-57Ds were built, the first making the variant’s maiden flight in November 1955. Incorporating extended and wider-chord wings of 106ft (32m) span and uprated Pratt & Whitney J57 engines of 11,000 lb static thrust each, the type entered service in April 1956, but served with the USAF for only five years.

The slender delta planform of the XB-70 Valkyrie, with large canards fitted to the forward fuselage, was similar to that of the CL-400-13. The unusual configuration utilised compression lift, in which the shock wave generated off the nose at supersonic speeds is used as a source of high-pressure air to generate additional lift.

The epitome of America’s bristling projection of global air power during the Cold War, Convair’s delta-winged four-engined supersonic B-58 Hustler strategic bomber (four General Electric J79 turbojet engines) made its first flight in August 1960. Capable of carrying a nuclear weapon in the centreline pod, the type also saw service in the photo-recce role as the RB-58.

Although a full-size airframe was never completed by Lockheed, the CL-400-10, codenamed Suntan, was clearly based on Clarence “Kelly" Johnson’s F-104 Starfighter design for the same company. The hydrogen-powered Mach 2-5-capable CL-400-10 was more than three times the length of its stablemate, however, and was to be fitted with specially-designed Pratt & Whitney Model 304 engines.

What might have been - this impression by IAN BOTT and NEIL FRASER imagines USAF and Lockheed groundcrew taking advantage of the cool pre-dawn desert air to prepare the huge but sleek CL-400-10 for another test flight from Area 51 in the early 1960s. The aircraft was nearly 165ft (50m) long with a wingspan of 83ft 9in (25 5m).

The CL-400’s P&W Model 304 engine