Martin 4-0-4

The Martin 4-0-4 is a pressurized, all-metal, low-wing airliner for about 40 passengers, built by the Glenn L. Martin Company and introduced in 1951. It was derived from the unpressurized Martin 2-0-2 after that type's wing structural failures, with a redesigned wing, pressurization, a slightly longer fuselage and two Pratt & Whitney R-2800 radial piston engines. Eastern Air Lines and Trans World Airlines took the first deliveries, 103 were built at the company's Baltimore factory, the United States Coast Guard flew two as the RM-1G and later VC-3A, and Southern Airways flew its last 4-0-4 service on 30 April 1978, the last piston-engine airliner flight by a major US carrier.