The Comet’s cabin was being pulled apart, one flight at a time
The de Havilland Comet, the first commercial jetliner to enter regular service, flew higher and faster than earlier airliners. Its pressurized cabin let passengers breathe comfortably at altitude—but every climb and descent loaded the fuselage in a repeating cycle. At altitude, cabin pressure pushed outward; after landing, that pressure was released. The metal flexed slightly each time.
That repeated loading can cause metal fatigue: tiny cracks form and gradually grow, even when the metal is not strained enough to break in a single flight. On the Comet, the cracks developed around the cabin windows and other openings. The original windows had nearly square corners, where stress gathered more intensely than along a smooth curve. Rivet holes near the corners added vulnerable points.
Why the failures were so sudden
A small crack could grow unnoticed until the remaining skin could no longer hold the cabin’s pressure. Then the fuselage could tear open rapidly, causing catastrophic structural failure. The crashes of two Comet 1 aircraft in 1954 prompted investigators to examine recovered wreckage and test the aircraft’s structure rather than treating each loss as an isolated accident.
In a major test, engineers repeatedly pressurized a Comet fuselage in a water-filled tank. The water made it possible to reproduce the pressure cycles while limiting the danger of an explosive air failure. The testing revealed how fatigue cracks could develop around the windows and eventually spread through the fuselage.
A design lesson written into every airliner
The Comet was grounded, and later aircraft incorporated changes including more rounded windows and stronger details around openings. The deeper lesson was not that pressurized flight was inherently unsafe, but that a cabin’s many small cutouts could determine how long its entire structure lasted. In modern aircraft, a window’s curved corners are part of the engineering that helps keep a tiny crack from becoming a sudden break.
