The Boeing Model 307 Stratoliner was the first fully pressurized airliner to enter service anywhere in the world. Being able to fly 20000 feet higher than the 5000 to 10000 foot-altitude unpressurized airplanes a that time, it was said that it could "fly above the weather." It carried five crew members and 33 passengers and had a nearly 12-foot wide cabin for overnight berths. The Stratoliner was also the first land-based airplane to have a flight engineer as a member of the crew. Boeing’s Model 299, prototype for the military bomber aircraft, which duly became the B-17 Flying Fortress, was developed in parallel with a civil version of the same aircraft, which had the company designation Boeing Model 300. The Model 307, or Stratoliner, was a straight-forward conversion from the supremely successful B-17 Flying Fortress bomber. It employed the wings and tail surfaces of the B-17C Flying Fortress. The Boeing 307 was developed to start another era, that of pressurized comfort at higher altitudes than had been previously contemplated. The aircraft was the result of considerable research in high altitude flying by "Tommy" Tomlinson, of TWA, who was estimated to have flown more hours above 30000 feet, than all other pilots combined. With his recommendations, Boeing produced an airliner which could cruise at 14000 feet. The Boeing 307 first flew on December 31, 1938, and TWA put it into service on the transcontinental route on 8 July 1940, reducing the time to 13 hrs. 40 min