Strato liner

On 23 July, there was a sight off the left wing of the T-6 camera plane that I thought I would never see. Roaring just above the tops of the low cloud deck was a Boeing Model 307 Stratoliner restored to magnificent pristine Pan American Airways specifications just like it had been over six decades ago when it was delivered to the airline. "That thing is just beautiful," said camera plane pilot Tim "Action" Jackson as we slid into formation with Clipper Flying Cloud as the airliner headed east.

Only ten Boeing Model 307s were built and Clipper Flying Cloud is the last survivor. How and why this large four-engine craft came to be in the Minnesota sky is an interesting story so let's go way back to the beginning.

Boeing had enjoyed considerable success during the 1930s with an innovative series of aircraft that helped pioneer all-metal aircraft construction. Boeing engineers knew that the day of the composite aircraft was drawing to a close - steel tube fuselages and wooden wings covered with fabric were giving way in the search for higher performance and this required newer forms of designing and building planes.

Boeing built the B-9, the Monomail, the Model 247, and the P-26 - all pioneering aircraft that utilized metal construction. The B-9 was the first all-metal cantilever monoplane bomber for the Air Corps. Produced only in limited numbers, the craft pointed the way to the future. Boeing engineers were quick to adopt new features such as retractable landing gear, NACA cowlings, and controllable pitch propellers that helped increase performance. The Monomail was very radical for the day with its sleek all-metal design, tightly cowled a engine, and retractable gear. The Boeing 247 was the world's first mod- ern airliner but its moment of glory would be short since it would be eclipsed by the Douglas DC-2 in just one year. The P-26 fighter, while hav- ing all-metal construction, was a bit of a throwback with its fixed landing gear but this was an Air Corps requirement.

And then there was the magnificent Model 299 - the company-funded prototype that would eventually evolve into the B- 17 Flying Fortress. Ahead of its time, the Model 299 nearly became a failure when the Air Corps opted to purchase large number of the Douglas B-18 Bolo which was a modification of the DC-2 and basically obsolete the day it was rolled from the Santa Monica factory. Fortunately, the military also ordered a small number of B-17s and with these aircraft the design was developed into America's first strategic bomber.

Boeing was never a company not to reuse a good idea. The Model 299 was closely examined as an airliner but this would not be a simple conversion of a bomber into a limited use airliner with a cramped passenger interior. The world of air travel was rapidly changing and Boeing once again wanted to take all the latest technology to create a new design while using some of the tried and true features of the Model 299. Stung by the brief reign of the Model 247, Boeing reasoned that the next generation of airliner would have to fly above the weather for more efficient performance and for passenger comfort. This would require the use of a pressurized fuselage - something that had not been done with a commercial aircraft. Lockheed had carried out important research with the pressurized XC-35, a modified Model 10. However, developing a pressurized airliner was truly breaking new ground. TWA pilot Tommy Tomlinson had, during 1935-1936, done lots of very high altitude flying in test aircraft such as the Northrop Gamma. During that period he accrued more flying time over 30,000 feet than all other pilots combined. During his meticulous testing, he concluded that the majority of weather problems ended at 16,000 feet and this information was factored into the new design.

Given the initial designation of Model 307, engineers busily began work on the specifications (which were settled on during December 1935) while the sales force concentrated on getting orders. This was the really difficult part since the aircraft was radical in its mission and it was also not cheap - being listed at $315,000 in 1938 (about $4,100,000 in today's dollars).

There was some interest in Europe but that started to decline as the threat of war with Hitler's Germany began to build. In America, there were really only two basic customers that could successfully operate the advanced plane - Transcontinental and Western Air and Pan American Airways. Both airlines had large route structures where a pressurized airliner could be fully utilized.

The order book was modest - Pan American opted for four aircraft while TWA wanted five. Some interest was being shown by KLM for their long routes to the Dutch East Indies but a surprise order came from a most unusual source. An increasingly reclusive Howard Hughes decided he wanted a Model 307 for a projected record flight but Boeing did not want to oblige, opting to satisfy operators rather than an individual. It is interesting to note that Hughes became the principal stockholder in TWA during April 1939 and his decisions would influence the direction of the airline for years to come.