In 1967, the smaller, short-range 737 twinjet was the logical airplane to complement the 707 and the 727. There was increasing demand for transports in its category, but the 737 faced heavy competition from the Douglas DC-9 and the British Aircraft Corp. BAC-111. The 737 had six-abreast seating -- a selling point, because this way it could take more passengers per load -- the DC-9 seated five abreast. The number of seats in the 737 also was increased by mounting the engines under the wing. This engine placement buffered some of the noise, decreased vibration and made it easier to maintain the airplane at ground level. By 1987, the 737 was the most-ordered plane in commercial history.