Stratoliner 75th Anniversary

January 22, 2014 in Commercial

It was introduced 75 years ago, and only 10 were built. Hollywood movie producer and aviation pioneer Howard Hughes bought one of them. But Boeing’s Stratoliner changed commercial aviation.

For the first time, passengers could “fly above the weather” at high altitudes because of the airplane’s pressurized cabin. The Stratoliner, the world’s first pressurized commercial airplane, was born in the 1930s, during a time of rapid evolution in the science and technology of flight, beginning with dramatic advancements in aircraft structures. Wood and fabric gave way to metal, monoplanes replaced biplanes and, before the decade was out, another great innovation would revolutionize flight—cabin pressurization.

Throughout the 1930s, pressurization experiments were taking place in Europe as well as the United States, where the U.S. Army was testing cabin pressurization with a modified Lockheed Electra designated XC-45. Boeing researchers were also experimenting with the technology and made it workable with the innovation of a cabin pressure regulator.

In 1932, Boeing had introduced the fast, all-metal Model 247, considered the first modern commercial airliner. It was a leap ahead of the competition, but its success was brief, as Douglas Aircraft quickly developed a challenger with the DC-2 and followed with the legendary DC-3. Faced with being shut out of the commercial airplane market, Boeing had to design the next leap in air travel.

Fortunately, Boeing had already developed the Model 299, a giant four-engine bomber that would become the B-17 Flying Fortress. The successful design of the B-17 became the basis for a new commercial airplane that would be that great leap: the Model 307.The new airplane combined the wings and tail surfaces from the B-17 with a cigar-shaped fuselage purposely designed to be a pressure vessel. Not only would its size, four engines, and long range be a market advantage, but the addition of cabin pressurization would allow Boeing to market an airplane that could fly passengers higher than 20,000 feet (6,100 meters)—“above the weather.” To reflect this capability Boeing named the Model 307 the Stratoliner.

Orders for the plane came in from Pan American Airways and TWA. Hughes also ordered a Stratoliner for his attempt at a world speed record. On New Year’s Eve in 1938, the Stratoliner prototype took off from Boeing Field near Seattle on its inaugural flight. Tragically, that prototype and a crew of 10 would later be lost in an airline demonstration flight.

But the Stratoliner’s success was short-lived. With the outbreak of war, Boeing turned to a maximum effort to build bombers and ended production after just 10 airplanes. During the war, Stratoliners were drafted into military service and made thousands of accident-free crossings of the Atlantic serving as VIP transports.

Only two Stratoliners remain: Howard Hughes’ personal Stratoliner is now a houseboat and continues to be a popular attraction in Florida; the last flyable 307, Pan Am’s Clipper Flying Cloud, was fully restored by Boeing and delivered in August 2003 to the National Air and Space Museum, where it is on display at the Stephen F. Udvar-Hazy Center in Chantilly, Va.