The Piggy-Back plane (more prosaically known as the Short Mayo Composite) was developed by Short Brothers (Shorts), a firm noted for its production of flying boats. Shorts’ flying boats could travel long distances if they could refuel en route, but the transatlantic route was rendered impossible unless passenger space was replaced with fuel tanks.
It was known that a plane could actually fly supporting a heavier load than that with which it was possible to take off. Major Robert H. Mayo of Imperial Airways proposed carrying a smaller, but heavier, plane into the air attached to the back of a larger, lighter plane. The thrust of both planes’ engines would lift them to the required height, after which they would separate, the larger one returning to base and the smaller one continuing on its journey.
In development, a launch plane named Maia carried the transport plane Mercury to its operational height. The first in-flight separation was on February 6 1938 and the first trans-Atlantic flight was on July 21 1938. The planes were prevented from colliding after separation by the design of the wings and the special three part locking system that held them together. A lock for each pilot released first and a final automatic lock that operated at the right moment.
Only one composite plane was built. Technological advances and the onset of WWII rendered it obsolete, and Maia was destroyed by German bombs in May 1941. Mercury was scrapped for its aluminium in August of that year.
Yet the idea didn’t entirely die. In 1976, NASA used it to transport the Space Shuttle between air bases, bolted onto a Boeing 747.
Text and curation: Amanda Uren