From Wikipedia:

The EWR VJ 101 was an experimental German jet fighter vertical takeoff/landing (VTOL) tiltjet aircraft. VJ stood for Versuchsjäger, (German for "Experimental Fighter"). The VJ 101 was one of the first V/STOL designs to have the potential for eventual Mach 2 flight.

During the 1950s, as various nations took an interest in developing VTOL-capable aircraft, the German Federal Government issued a request to the nation's recently revived aviation industries for them to study possible designs for such aircraft. In response, in 1960, German engine manufacturer MAN Turbo commenced work on a suitable engine in close cooperation with British engine manufacturer Rolls-Royce Limited. Likewise, aircraft firms Heinkel, Bölkow and Messerschmitt performed their own studies before coming together to form a joint venture company, EWR, for the purpose of developing and manufacturing their design for a supersonic VTOL fighter aircraft, which was soon designated as the VJ 101 D. The Federal Ministry of Defence (BMVg) were suitably impressed to place an order for a pair of experimental prototypes to be produced to demonstrate the design's capabilities.

A pair of prototype aircraft, collectively known as the VJ 101 C and individually known as the X-1 and X-2, were constructed and participated in a five-year test program. The intention was for the VJ 101 to eventually be developed as the basis for a successor for the German Air Force's inventory of American Lockheed F-104G Starfighter interceptors. However, development of the VJ 101 C was greatly complicated by the changing requirements of the BMVg, who decided to transform the aircraft's envisioned mission profile from the interceptor role to a more general fighter instead, greatly changing the performance requirements for it to fulfil. During 1968, development of the VJ 101 was ultimately cancelled.