[5] Each company contributed $100,000[notes 1] to development costs and agreed to not operate other aircraft with a maximum weight of 43,000 to 75,000 lb (20,000 to 34,000 kg) for revenue service.

[3] The crash delayed the program by over a year, beginning with a three-month investigation by the US Civil Aeronautics Authority, the precursor to the current Federal Aviation Administration, and Boeing to determine the causes.

[30] Both used three bladed Hamilton Standard Hydromatic constant speed propellers,[26] and new high octane fuels were developed to help the engines operate under the increased supercharger pressure.

[26] On most, but not all examples, the leading edges of the wings, horizontal stabilizer and fin were fitted with rubber expanding type de-icing boots, which would inflate and deflate repeatedly to break ice from the flying surfaces.

[26] All movable surfaces, including the rudder, ailerons and elevators had fabric over a metal structure, and were aerodynamically balanced and fitted with adjustable trim tabs to lighten flight loads.

Its walls were covered in heavy plate glass mirrors, and it contained in its 34 sq ft (3.2 m2) area two dressing tables, each with a sink, plush upholstered stools, soft indirect lighting provided by fluorescent lamps, ashtrays, hot and cold running water, shelves with towels, and a separate cubicle for the toilet.

[34][38] Extensive use was made of the latest in sound proofing, and the Dynafocal engine shock mounts were designed to reduce vibrations from being felt by the passengers.

[40] Following the entry of the United States into World War II in December 1941, long-range transports were needed to ferry government and military officials around the globe and many aircraft, including T&WA's Boeing 307s, were pressed into service.

A 400 ft (120 m) trailing wire antenna was used with a 5 lb (2.3 kg) lead weight on the end - which the radio operator needed to remember to reel in, by hand, when landing.

[41] The landing gear was strengthened, and the maximum takeoff weight was increased from 45,000 to 56,000 lb (20,000 to 25,000 kg), leaving the Stratoliner underpowered, and the climb suffered accordingly.

[42] The exterior was then camouflaged in standard USAAF colours, with olive drab upper surfaces and neutral grey undersides,[10][45] and each aircraft had its name painted on the nose and over the cabin door, which would also be used by many later operators.

[48] Further mods made by TWA included improved sound proofing and temperature control,[49] and on March 15, 1945, the B-1 recertification tests were completed to the CAA's satisfaction.

[30] They required that it fly on just two engines, use Pratt & Whitney automatic mixture controls, have a 2,500 mi (4,000 km) range, be able to carry freight or mail, and have moderate tire ground pressure.

[30] KLM then requested a quote for three 307s, either with Wright Cyclones and with Pratt & Whitney 1830 engines, fitted with constant speed propellers and automatic carburettor mixture control and with additional fuel to provide a range of 3,400 mi (5,500 km).

[6] He bought aircraft serial number 1997[61] registered as NX19904 for $315,000[notes 5][62] for a round-the-world flight, hoping to break his own record of 91 hours 14 minutes set between July 10 and 14 in 1938 in a Lockheed Model 14 Super Electra.

[63] Hughes had the extra fuel tanks removed, and for around $250,000,[notes 6] he had it fitted with much more powerful Wright R-2600 engines for its transformation into "The Flying Penthouse", which included a Master Bedroom, two bathrooms, a galley and a bar as well as a living room.

[64] It was then bought for $69 by Kenneth W. London, who cut the damaged wings and tail off, built a hull under it, and installed a pair of V-8 engines to convert it into a houseboat which he named Londonaire.

[2] The main route was La Guardia, NY to Chicago, Illinois to Kansas City, Missouri to Albuquerque, New Mexico to Burbank California and the reverse.

[70] and a few weeks later, on September 26, a TWA New York bound Stratoliner at 17,000 ft (5,200 m) with a jetstream providing a strong tailwind reached a ground speed of 387 mph (623 km/h).

[78] The first north Atlantic crossing was in March 1942, when a flight from Washington to Prestwick carried senior military and government officials to Europe, which included the Army Chief of Staff General George C. Marshall, General Dwight D. Eisenhower (to command Operation Torch for the invasion of North Africa), Deputy Chief of Staff of Army Ground Forces General Mark W. Clark, Operation Torch Air Force liaison officer Colonel Hoyt Vandenberg, Chief of the Navy's Bureau of Aeronautics Rear Admiral John Henry Towers, who oversaw Navy aircraft procurement and training, and presidential advisors W. Averell Harriman and Harry Hopkins who were crossing to negotiate the lend-lease program.

[79] In November 1943, a C-75 carried Soong Mei-Ling, wife of the Chinese Nationalist warlord Chiang Kai-Shek, from Chungking to Washington to receive medical care and to negotiate military aid for China.

[84] Cherokee was returning American troops from Reykjavik to Gander at 1,000 ft (300 m), and was shot at by a US Navy ship that left over 200 holes in the aircraft's tail, and which nearly severed the elevator controls.

[76] By 1944 the USAAF had enough long range transports that it no longer needed the small number of C-75s it had, and sold the fleet back to TWA, with the aircraft being transferred between January 6, 1944, and December 19, 1944.

[86] On July 10, 1939, TWA had signed a contract with Lockheed to develop the Constellation, which was to be capable of 5 miles/min (350 mph (560 km/h)) compared to the Stratoliner's 4 miles/min (246 mph (396 km/h)),[8] but with production diverted to military for the duration of the war, the first TWA Constellations did not enter service until February 1946 and were soon grounded dealing with the usual teething problems encountered with a new type, from July 11 to September 20, 1946, while the Douglas DC-4s began arriving in 1946 in small numbers and the Douglas DC-6 similarly, from 1947.

It had departed from Tan Son Nhat International Airport in Saigon and was heading for Vientiane when the number four engine had to be shut down, and when it returned to land, it overshot the runway in deteriorating weather, and a violent squall or microburst blew it sideways, causing it to hit the ground.

Airnautic (or Air Nautic) received three ex-Aigle Azur SA-307B-1s in 1955 and 1956 including, F-BELU,[101] F-BELY,[102] and F-BELZ,[103] which were operated in southern Europe around the Mediterranean providing charter flights, especially around Corsica.

On December 29, 1962, F-BELZ collided with a mountain while on a charter flight with 22 basketball players and fans while flying from Bastia to Ajaccio, on the island of Corsica.

Compagnie Internationale de Transports Civil Aériens (CITCA) bought five Stratoliners, F-BELU F-BELV F-BELX F-BELY F-BELZ, which were leased out to other operators.

[107] XW-TFR (previously F-BELX and briefly XW-TAB) had been returned to Cambodia Air Commercial when it was destroyed in an accident on June 27, 1974, following three of the four engines failing while climbing out from Battambang Airport.

The aircraft was awaiting restoration at Fort Lauderdale International Airport in August 1964 when it was severely damaged when Hurricane Cleo tore it loose from its tiedowns, and it was blown into a stand of trees.