Sabena airliners which were augmented and later replaced by Douglas DC-6Bs. The DC-4s also restarted the airline's traditional route to the Belgian Congo. Sabena was the first airline to introduce transatlantic schedules from the north of England, when one of its DC-6Bs inaugurated the Brussels-Manchester-New York route on 28 October 1953. The Convair 240 was introduced in 1949 to partially replace the DC-3s that until then had flown most European services. As of 1956, improved Convair 440 "Metropolitan" twins began replacing the Convair 240 twins and were used successfully well into the 1960s between European regional destinations. In 1957, the long-range
National Airline History Museum Martin 4-0-4s built. TWA operated 40 in their fleet along the U. S. east coast, while strong competitor Eastern Airlines operated the largest 4-0-4 fleet, flying 60 aircraft along that airline's eastern seaboard route, including in and around Florida. The museum's Martin 4-0-4 has not flown in years. As part of the National Airline History Museum’s reorganization plan, which began in 2011, a maintenance inspection of the Martin 4-0-4 was completed in August 2011 to determine the feasibility of returning the aircraft to flying status. Rumors of extensive corrosion and insurmountable mechanical problems were found to be untrue, and a