Three-engined jetliners were in vogue in the fuel-conscious early 1970s, and for a while'three lumps' instead of'four' looked like the way ahead for wide-body jetliners, particularly as far as McDonell Douglas and Lockheed were concerned. However, the advent of more fuel-efficient powerplants has seen operators opt for either two- or four-engined designs, and today only the MD-11 remains in production, giving its manufacturer a toe-hold in the world's widebody jetliner business.