The recession of 1969-1970 was very bad for Boeing. For over a year after September 1970, it only sold two 747s. None were sold to an American airline for over three years. Some airlines did not have enough passengers to fly the 747. Therefore, they replaced them with the McDonnell Douglas DC-10 and Lockheed L-1011 TriStar. American Airlines eventually only used its 747s to carry cargo. In 1983, AA gave its 747s to Pan Am. Pan Am gave American Airlines some smaller planes. Delta Air Lines also stopped using its 747s after many years. Delta would later merge with Northwest Airlines, which operates 747s.