The McDonnell Douglas MD-11 is a wide-body aircraft produced by McDonald Douglas and equipped with three engines. Its design is derived from the DC-10 aircraft and features one engine on the tail wing. But its fuselage and wingspan are longer than DC-10, and small wings are also installed at both ends of the wings, and the design of the wing section has also been improved. The MD-11 provides new engines for buyers to choose from, uses more composite materials, and the cockpit equipment is fully digitized. After the discontinuation of production in 2001, many MD-11 aircraft were used for freight services, and all retired MD-11 aircraft were also converted into cargo aircraft.