In June 1939, Howard Hughes, the owner of Transcontinental & Western Air (later Trans World Airlines and abbreviated TWA), held a meeting at his Hancock Park residence in California.

Jack Frye (then president of TWA) attended along with three executives from the Lockheed Aircraft Corporation which included designer Clarence "Kelly" Johnson.

Six different layouts of the cockpit envisaged, including a "Bug-Eye" proposal in which the pilot and co-pilot would sit in separate domes next to each other.

A complete life sized mock up of the Excalibur was eventually constructed with battery operated retractable landing gear.

[1][2][3] A few months before the United States entered World War II, the Wartime Production Board inspected Lockheed's Burbank facility which housed the Constellation prototype.

On December 7, 1941, Japanese forces launched a surprise attack on the US Naval base in Pearl Harbor, Hawaii, causing the United States to enter the war.

In March 1942,[4] the 80 L-049 Constellations planned for airline use were requisitioned by the Air Transport Command, and given the military designation C-69.

On April 17, 1944, the second production C-69 was flown by Howard Hughes and Jack Frye, President TWA [5] on a flight between Burbank and Washington DC that took little less than seven hours.

As World War II drew to a close, large quantities of military surplus became available on the civilian market along with the cancellation of the remaining C-69 Constellations still in production.

With the Constellation's design at risk, Lockheed purchased the five remaining C-69 transports still in production back from the military, saving 15,000 jobs.

These modifications included removal of the retractable tail stand; along with the inclusion of a luxury interior, more portholes, a galley, and crew relief areas.

Design tests did not need to be conducted, as Lockheed had already tasked them to the C-69 aircraft during the war (one of the C-69s also completed the trials for the civilian airworthiness certificate on December 11, 1945).

This made the development of L-049 months ahead of the competing Boeing 377 Stratocruiser, Douglas DC-6 and Republic RC-2 Rainbow (which was still on the drawing board).

On January 14, 1946, Pan Am began flying its L-049 equipment between Bermuda and New York, replacing the slower Boeing 314 Clipper that flew before it.

On the evening of June 18, 1947, the Lockheed L-049 Constellation serving Pan Am Flight 121, known as the Clipper Eclipse and crewed by third officer Gene Roddenberry (who went on to create the original Star Trek television series), suffered an engine failure which led to the overheating of the remaining engines until one caught fire, which spread to the aircraft.

When an engine fell from the aircraft, it was unable to maintain altitude, resulting in a crash in the Syrian desert 4 miles (6.4 km) from the town of Mayadin in the early morning of June 19, 1947 and the death of fifteen people.