The 747-400 was the next-generation Boeing 747 introduced in 1989. It is the best-selling variant of the Boeing 747. It includes improvements over the 747-300 including new engines, and new winglets, which improve fuel efficiency. Its length is the same as the 747-300 but the wingspan has been increased to 211 feet 5 inches. The 747-400 retains the same longer upper deck as the 747-300 (excluding frieghter versions), and came in six variants: the 747–400, 747-400F, 747-400M, 747-400D, 747-400ER, and the 747-400ERF.