During the 1960s and 1970s, Boeing had seen success with the Boeing 707 and 727, and there was growing interest from airlines in a more economical two-engine option. The 737 performed its first flight in 1967 and has, as we know, gone on to be the most delivered aircraft to date. Other manufacturers tried to compete, though, with varying success. The French-built Dassault Mercure was one such competitor. Only 12 aircraft were ever built, with the French airline Air Inter being the only operator.