Where does this come from, and can I check it?

Twin engine airliners are cleared in minutes of flying time from a usable diversion airport, not in distance. The figure is taken from Federal Aviation Administration, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

Is this really a technology fact?

Yes. It sits on the Technology shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

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The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.

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ETOPS rules measure how far a twin may stray

Twin engine airliners are cleared in minutes of flying time from a usable diversion airport, not in distance Extended range twin operations began as a restriction and became a selling point when the Boeing 767 gained 120 minute clearance in 1985. The rating sets how long an aircraft may be from a suitable runway with one engine running. Four engine jets were once preferred for ocean crossings largely because of this limit. It sits in Mondo's technology collection, one of 200 facts that each trace back to the reference below.

Where this comes from

Federal Aviation Administration

Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.

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Tags: aviation, safety, regulation

ETOPS rules measure how far a twin may stray: the short answers

Where does this come from, and can I check it?: Twin engine airliners are cleared in minutes of flying time from a usable diversion airport, not in distance. The figure is taken from Federal Aviation Administration, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a technology fact?: Yes. It sits on the Technology shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.