Deliveries of the MD-11, a wide-cabin trijet, began in 1991 and continued until Feb. 22, 2001, four years after the McDonnell Douglas Corp. merged with The Boeing Company. The MD-11 was available in four models: passenger, all freighter, convertible freighter and "combi," where passengers and freight were carried on the main deck and additional freight below the deck. An extended-range (ER) feature was available on all versions.