Boeing isn’t the first manufacturer to miss critical problems when certifying a new aircraft.

Frenzied headlines aside, the recent Boeing 737 MAX crashes fit a long pattern in the imperfect history of aircraft-certification programs, which sometimes miss fatal flaws.

Start with the de Havilland Comet, made in Britain. While the Boeing 707 popularized jet travel, the Comet was the world’s first commercial jetliner, entering service in 1952.

Less than two years later, a Comet broke apart 20 minutes after taking off from Rome and plunged into the Mediterranean for undetermined reasons. The fleet was grounded temporarily, but a few months later a second Comet broke up over the sea. This time the fleet was grounded permanently, and the aircraft was extensively redesigned to combat a problem then little understood: metal fatigue.

The aircraft-certification program had failed to detect that. It hadn’t known what to look for.

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