Forty years ago, an Atlantic crossing required four engines because twin-engine certification kept you within an hour of a diversion airport. Today twin-engine 777s and A350s fly six hours over open ocean, and three- and four-engine widebodies are nearly extinct. We walk the ETOPS framework, the engine-reliability math behind it, the route history that opened up, and the honest reason economics finished the job certification started.
Etops
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Why Airliners Are Twin-Engine Now