The Boeing Model 307 Stratoliner was an American commercial transport aircraft that entered commercial service in July 1940.
It was the first to offer a pressurized cabin, allowing it to cruise at an altitude of 20,000 ft (6,000 m), well above many weather disturbances.
The pressure differential was 2.5 psi (17 kPa), at 14,700 ft (4,480 m) the cabin air pressure was equivalent to an altitude of 8,000 ft (2,440 m).
The Model 307 had capacity for a crew of six and 33 passengers.
The cabin was nearly 12 ft (3.6 m) across.
It was the first land-based aircraft to include a flight engineer as a crew member
(Several flying boats had included a flight engineer position earlier).
In addition to its civilian service it was also flown as the Boeing C-75 Stratoliner by the United States Army Air Forces, who used it as a long range cargo lift aircraft.
Variants
300
Original concept designation of 307.
307
Equipped with Wright Cyclone GR-1820-G102 engines with single-speed supercharger, five crew.
307B
Equipped with Wright Cyclone GR-1820-G105A engines with two speed supercharger for improved high altitude performance, seven crew.
C-75
Five Trans World 307Bs were pressed into service with the USAAF as military transports, the cabin pressurization was removed to save weight.
307B-1
Following military service, the C-75s were overhauled and updated with B-17G wings and tail plane, four Wright Cyclone GR-1820-G606 engines, and B-29-type electronics.
