In the early 1960s, the West German government presented aircraft manufacturer Dornier with a daunting challenge. Concerned that a conflict might destroy existing runways and render its airfields unusable, authorities asked Dornier to develop a vertical takeoff and landing (VTOL) transport aircraft. With significant experience developing unconventional aircraft, Dornier rose to the challenge and began designing what would become the Do-31, a transport jet capable of carrying 36 troops at speed up to 351 knots at 35,000 feet.
At the time, jet-powered VTOL aircraft had successfully flown, but all were smaller tactical and experimental types. Hawker had successfully built and flown the P.1127, which evolved into the Harrier attack aircraft. Other manufacturers had built similarly small VTOL jets, such as the Dassault Balzac V, the Short SC.1, and the EWR VJ 101. But no manufacturer had successfully integrated VTOL capability with a cargo platform.
