On 14 June 1954, a de Havilland Comet 1, operated by British Overseas Airways Corporation (BOAC) as Flight 781, crashed into the sea near the island of Elba while en route from Rome to London, killing all passengers and crew aboard. The Comet had been the world’s first commercial jet airliner, introduced with great public attention and hailed for its speed and modernity. The accident, followed by subsequent Comet losses, became a turning point in civil aviation safety because it exposed previously unrecognized structural vulnerabilities in pressurized jet airframes. What happened: Flight 781 took off from Rome’s Ciampino Airport and disappeared from radar shortly after passing over the eastern Mediterranean. Wreckage and bodies were later recovered from the sea near the Italian coast. Initial reports noted that the airframe had broken up in flight rather than suffering a survivable ditching or controlled impact. The sudden in-flight breakup and the lack of any distress call suggested a rapid catastrophic failure. Investigation and findings: British investigators led by the Accidents Investigation Branch, working with de Havilland engineers and other experts, faced the difficult task of determining the cause from fragmented wreckage recovered from the seabed. The investigation methods included detailed examination of recovered pieces, pressurization tests on Comet fuselage sections, and laboratory simulations. Their work eventually identified metal fatigue cracks originating at square-shaped passenger window corners and other stress-concentrating features. Repeated pressurization cycles in commercial service caused cracks to initiate and propagate unnoticed until catastrophic failure occurred. Consequences for aircraft design and safety: The findings prompted major redesigns of the Comet and influenced worldwide aircraft engineering. Square windows were replaced by oval or rounded shapes to reduce stress concentration. Structural testing procedures and fatigue analysis became standard practice, and investigators emphasized the importance of full-scale pressurization testing and better understanding of high-altitude operating stresses. The accidents also led to improvements in wreckage recovery and investigative technique, establishing methods that remain part of modern aviation accident investigation. Context and legacy: The Comet disasters underscored the risks of early adoption of novel technologies without fully understood long-term effects. While the de Havilland Comet program eventually resumed with redesigned models, its early commercial lead was lost to competing manufacturers who incorporated the lessons learned. The investigations into the 1954 crash and related incidents are credited with shaping contemporary aviation safety culture by demonstrating how systematic engineering analysis and rigorous testing can prevent repeat tragedies. Uncertainties and sources: Specific details about the sequence of structural failures and the exact propagation of fatigue cracks were reconstructed from recovered wreckage and laboratory tests; some finer points remain technical and were debated during the inquiry. Contemporary reports and the official accident investigation reports from the United Kingdom provide the primary historical record of the event and its conclusions.