On 10 January 1954, BOAC flight 781 left Rome for London and broke apart in the air twenty minutes later, falling into the Mediterranean near the island of Elba. All 35 people aboard died. It was the first of the in-flight break-ups that would ground the de Havilland Comet and, indirectly, hand the jet airliner market to the United States.
The immediate response
The Comet was Britain's national achievement — the first jet airliner in service, two years ahead of anyone else, and a matter of considerable prestige. The aircraft was grounded and inspected. With no obvious cause available and no wreckage recovered at that point, the investigation could only theorise: engine turbine failure, an uncontained fire, sabotage.
Modifications were made addressing several of these hypotheses, and BOAC returned the Comet to service in March. Two weeks later, South African Airways flight 201 broke up in almost identical circumstances after also departing Rome. The Comet's certificate of airworthiness was withdrawn, this time for good.
Raising the wreckage
What followed was remarkable for 1954. The Royal Navy conducted a salvage operation to recover wreckage from the seabed off Elba — deep, difficult work with the technology of the day. Roughly two-thirds of the aircraft was eventually raised and taken to Farnborough, where it was reassembled on a wooden frame.
The reconstruction let investigators trace the sequence backwards: the break-up had started in the cabin structure, not the engines and not from an external explosion.
The water tank
In parallel, a complete Comet fuselage was placed in a purpose-built water tank and cycled repeatedly between pressurised and unpressurised, simulating flights. After the equivalent of several thousand cycles the structure failed, with the crack originating at the corner of a cutout in the skin.
The cause was metal fatigue at points of stress concentration — a phenomenon understood in principle but badly underestimated for a fuselage cycling to high altitude several times a day. The Comet's window and hatch openings had corners sharp enough to concentrate stress until cracks grew and the structure failed catastrophically.
What it produced
The findings from BOAC 781 and its sister accident produced the rounded cabin window, full-scale fatigue testing as a certification requirement, and the damage-tolerance design philosophy that assumes structures will crack and requires cracks to be found before they become critical.
Britain published everything. Boeing and Douglas incorporated the findings into the 707 and DC-8, both then in development. Those aircraft were safer because the Comet failed first and because the investigation was shared rather than buried.
The Comet returned as the redesigned Comet 4 and flew for years, including the first transatlantic jet passenger service. But two years grounded had cost it the market. The aircraft that opened the jet age was overtaken by the aircraft that learned from its failure.