On new-years eve, 1966, the federal government (of the US) elected Boeing to design the nation's first SuperSonic Transport, or SST.
The amazing result was that 26 airlines placed orders for 122 ships, each being 318 feet long with four 60,000 pound thrust engines. The jet was designed to cruise at 60,000 feet at Mach 2.7.
In 1971 Congress voted down further funding for the project, before the prototype was completed. A full-scale model remains somewhere, in pieces. The original design would have had variable-geometry wings, but the final result was fixed delta-wing, like the Concorde.
Obviously, the jet never flew.