Sixty-five years ago, on May 2, 1952, aviation history was made when a de Havilland Comet departed London for Johannesburg, South Africa—the world’s first passenger jet air service. It was a proud moment for Britain and its aircraft industry.
Post-war air travel was dominated by the American-made Lockheed Constellation and Douglas DC-6, and airlines—including British Overseas Airways Corporation, the UK’s flagship international carrier–lined up to buy them. British manufacturers made a bold decision to leapfrog over the piston-powered, propeller-driven American airliners by adopting turbine power. England led the United States in wartime jet engine technology, and hoped to take advantage of this by beating America with the first jet transport.
The result was the Comet, first flown in 1949, designed to show the flag serving destinations in the Middle East, Africa and the Far East. Its four de Havilland Ghost jet engines made the Comet 100 miles per hour faster than the American propliners in the thin air above 30,000 feet, but burned prodigious amounts of fuel to produce modest thrust. As a result, the Comet was small—initially carrying only 36 passengers—and lacked transoceanic range. Intended to link the outposts of the British Empire, flying between stops less than 2,000 miles apart, its economics required premium fares and well-heeled passengers. But de Havilland was working on an improved Comet, with more power, range, and passenger capacity, as well as more advanced versions with transatlantic capability. Airlines around the world—including the United States—took note, and placed orders.
Shortly after departing Rome in January, 1954 a BOAC Comet exploded in mid-air and fell into the sea. BOAC immediately grounded its Comet fleet for examination, and after making modifications, returned them to service in March, 1954. Less than a month later, another Comet exploded and fell into the ocean after leaving Rome. Once again all Comets were grounded, and the certificate of airworthiness was withdrawn. The most intense and difficult air accident investigation in history up to that time was undertaken, without the benefit of the black box data recorders considered vital in crash investigations today.
Detailed examination of wreckage recovered from the sea floor established that the fuselage structure had failed catastrophically near a window. A Comet fuselage was submerged in a large water tank and subjected to repeated pressurization cycles. After 1,800 cycles, the structure burst. The failure was traced to a crack which formed at a window resulting from metal fatigue. The investigation concluded that the cause was stress concentrations at the corners of the Comet’s square-shaped windows.
The Comet cruised at altitudes far higher than any other airliner of its time, necessitating higher pressure to maintain a safe and comfortable cabin environment. When it was designed no body of engineering knowledge was available on the structural effects of repeated flights, and pressurizations, at the Comet’s cruising altitude.
The learning gained from the Comet investigation resulted in new design principles which were applied to the Comet and other jet airliners. Oval windows, or rounded corners, were adopted to avoid stress concentrations. Structural design practice was revised to prevent small cracks from propagating. And a fail-safe approach was followed to allow cracks to be contained until they could be found by inspection and repaired before a catastrophic failure could occur.
A greatly improved Comet emerged from the 1954 accidents. Its fuselage was stretched to hold 90 passengers, and new, more powerful jet engines allowed it to cross the Atlantic non-stop. BOAC inaugurated Comet service between London and New York in October, 1958, cutting the flight time in half to six hours.
The Comet’s commercial prospects suffered from the four-year delay necessitated by its redesign. In 1954 Boeing flew the prototype 707–larger, faster and more economical to operate than the Comet–and flood of airline orders followed. Pan American Airlines’ transatlantic 707 services began a month after BOAC’s Comets, and the 707 went on to dominate and define the early jet age. The speed, comfort and safety of jets quickly swept propeller driven airliners aside.
The Comet went on to a successful airline career, and military derivatives operated well into the 21st century. The lessons learned from its tragedies paved the way for fast, cheap, reliable, and safe jet air travel, which brought the world together long before the internet. 
For more information about Husch Blackwell’s Aviation practice, click here.
 References: C. Martin Sharp, DH: A History of de Havilland (Airlife Publishing, 1982); Sam Howe Verhovek, Jet Age: The Comet, the 707, and the Race to Shrink the World (Penguin, 2010); Aerospace Engineering, Milestones in Aircraft Structural History, “The DeHavilland Comet Crash” (June 9, 2012), http://aerospace engineeringblog.com/deHavilland-comet-crash/.