The de Havilland Comet was the world's first jet airliner — and it broke apart in flight

The de Havilland Comet, which entered service in 1952, was the world's first commercial jet airliner. It was a technological triumph: faster, smoother and more comfortable than propeller aircraft. Britain's aviation industry was proud of the Comet as a symbol of post-war engineering leadership.

But in 1954, two Comets broke apart in flight at cruising altitude, killing all passengers and crew. The investigation, led by the Royal Aircraft Establishment, was one of the first major aviation accident investigations. The cause was metal fatigue: the repeated pressurization and depressurization cycles caused cracks to grow from the corners of the square windows and around rivet holes, until the fuselage failed.

The Comet was grounded and redesigned with rounded windows and reinforced structure. But the delay allowed Boeing and Douglas to enter the jet market with the 707 and DC-8, which incorporated the lessons from the Comet's failures. The case illustrated how a pioneering technology can reveal failure modes that the existing engineering knowledge does not anticipate, and how the pioneer's accidents become the competitor's education.