The Lockheed C-133 Cargomaster was a large turboprop airliner built between 1956 and 1961 by the Lockheed Aircraft Corporation.

   It began as a U.S. Air Force project for an intercontinental freighter with 35 to 40 tons (70,000 to 80,000 lb) of cargo and 48 passengers; it ended up as a 100-ton (200,000 lb) freighter able to carry more than twice that load over short distances.

   The Cargomasters went directly into commercial service after being delivered to the Air Force with little fanfare and remained in operation for nearly 20 years.

   Only 55 were built but the airplane had an extensive career spanning 21 years.

   The first flight of the XC-133 was on December 28, 1953.

The first prototype crashed during a test flight on May 4, 1955, killing Lockheed’s chief test pilot and 13 others. A second C-133A aircraft (serial number 53-3456) was built as an insurance risk and first flew on December 28, 1955. In late 1957, this aircraft was delivered to the Air Force as a C-133A but was diverted to Edwards AFB where it spent more than 10 years performing various test duties. It last served with the 436th Airlift Wing at Dover AFB, Delaware as a maintenance trainer before being retired in September 1976.

   The Cargomaster was a high-wing cantilever monoplane powered by four 18-cylinder radial Wright R-3350 engines, each engine driving a set of three-bladed reversible pitch propellers. It had a cargo compartment 36 ft (11 m) long, 9.5 ft (2.9 m) high, and 13.5 ft (4.1 m) wide, with a loading ramp in the rear that could be lowered to accommodate oversized cargo. It had a cruise speed of 350 mph (563 km/h), faster than any other turboprop airliner, so fast it could cross the United States from New York to Los Angeles in about four hours.