On 2 May 1952, a slim silver aircraft with four jet engines buried in its wing roots lifted away from London Airport, bound for Johannesburg with fare-paying passengers aboard. The de Havilland Comet was the world's first commercial jet airliner, and it made everything else in the sky look agricultural. It cruised at close to 500 miles per hour, roughly eight miles up, above the weather, in a cabin so smooth that passengers stood coins on edge to show off the absence of vibration. Piston airliners droned along at barely half the speed and half the height; the Comet cut long-haul journey times almost in half. Britain, whose aircraft industry had been overshadowed by America's since the war, suddenly held a lead that looked to be measured in years.
That lead rested on an unforgiving piece of physics. A jet only flies economically where the air is thin, and to carry people that high the cabin must be pumped up like a balloon — the Comet's fuselage was pressurised to a differential roughly twice that of earlier airliners. Every flight inflated the aluminium tube; every descent let it back down. No airliner had ever been asked to breathe in and out like that, thousands upon thousands of times across a working life, and the science of what repeated stretching does to thin metal skin was far less mature than anyone believed.
The fleet's luck curdled quickly. Take-off accidents in 1952 and 1953 were blamed on the wing's behaviour at high angles, and in May 1953 a Comet broke up in a violent storm shortly after leaving Calcutta. Then came the catastrophe that could not be explained away: on 10 January 1954, BOAC Flight 781 — the aircraft registered G-ALYP, "Yoke Peter", the very machine that had flown the inaugural 1952 service — disintegrated in clear morning air near the island of Elba, killing everyone aboard. The fleet was grounded while dozens of precautionary modifications were made, and services resumed within weeks. On 8 April 1954 a second Comet, flying for South African Airways, fell out of the sky near Naples. The type's certificate of airworthiness was withdrawn, and Britain's jet age stopped dead.
The tank at Farnborough
What followed was forensic engineering on a scale never attempted before. The Royal Navy dredged and trawled fragments of Yoke Peter from the Mediterranean seabed — a pioneering feat of deep-water salvage — and the shattered fuselage was pieced back together on a skeleton frame at the Royal Aircraft Establishment at Farnborough, under the direction of Arnold Hall. Alongside the reconstruction, Hall's team took a complete sister aircraft, G-ALYU, and sealed its fuselage inside an enormous tank of water. Water was pumped in and out to mimic the pressurisation of flight after flight, while hydraulic jacks flexed the wings; water was chosen because a pressurised cabin bursting in air explodes like a bomb and destroys the evidence, whereas in water it fails quietly. After the equivalent of around 3,000 pressurised flights, the cabin split open. The tear began at the corner of a cutout in the fuselage — metal fatigue, a crack growing invisibly with every cycle until the skin could no longer hold.
Popular memory has compressed all this into a single phrase: the Comet's "square windows". The record is subtler. The windows were squarish with rounded corners, and the tank failure actually started at an escape-hatch cutout, while the Elba aircraft's break-up was traced to a cutout in the cabin roof. The true villains were stress concentrations at the corners of openings in a skin built thin to save weight, aggravated by punched rivet holes that acted as ready-made crack starters. The fix — generously rounded openings, thicker skin and fail-safe structures designed to tolerate cracks — is why every airliner window you have ever looked through is oval.
The public inquiry under Lord Cohen laid the findings bare, and de Havilland shared the hard-won fatigue data openly with the world's manufacturers, including its American rivals; Boeing and Douglas absorbed the lessons into the 707 and DC-8. The redesigned Comet 4 flew the first transatlantic jet passenger service in October 1958, beating Pan Am's 707 across the ocean by a matter of weeks — but the moment had passed, for the American jets were bigger, cheaper to run and ordered in their hundreds. The Comet's airframe found a long afterlife as the RAF's Nimrod patrol aircraft, which flew until 2011. The airliner that fell from the sky ended up teaching the whole industry how to stay in it — and its memorial is the rounded window beside every airline seat on Earth.
Quiz nuggets
- The de Havilland Comet flew the world's first commercial jet airliner service on 2 May 1952, from London to Johannesburg for BOAC.
- Two 1954 break-ups — near Elba on 10 January and near Naples on 8 April — grounded the fleet for good.
- Investigators at Farnborough, led by Arnold Hall, pressure-cycled a Comet fuselage in a water tank until it failed after the equivalent of about 3,000 flights.
- The cause was metal fatigue cracking from the corners of cutouts in the pressurised cabin — remembered, a little inaccurately, as the "square windows".
- The Comet 4 flew the first transatlantic jet service in October 1958, weeks ahead of the Boeing 707, and the airframe served on as the RAF Nimrod until 2011.