Also, up until relatively recently regulators wouldn't let twin engines fly transoceanic flights because they deemed it too risky. They added ETOPS[1] regulation in order to allow this
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Prior to this change you needed 3 or more engines to cross large bodies of water or ice. When ETOPS was revised the abbreviation was backronynmed to "Engines Turn Or Passengers Swim".
This is important, ETOPS regulation changes are a big reason twin jets are resurging