ETOPS

ETOPS () is an acronym for Extended-range Twin-engine Operations Performance Standards (or sometimes Extended Twin Overwater Passenger Service). These are safety standards set by the International Civil Aviation Organization (ICAO) for twin-engine commercial passenger aircraft operations. They are a safety measure intended to ensure that in the event of a single engine failure, an aircraft will still be able to reach a diversion airport using the remaining operational engine, albeit at a reduced speed or altitude. The standard typically applies to long-distance routes over water or remote areas, which were historically restricted to three- and four-engine aircraft.

Twin-engine passenger airliners are typically restricted to areas within a one-hour flying time of a suitable airport on one operational engine. ETOPS-90 certification extends this to a 90-minute flying time, ETOPS-180 to 180 minutes, etc.

Similar limits have since been applied to three- and four-engine airliners. In some cases, "ETOPS" is still used to refer to these rules, but other terminology has been introduced to remove "twin" from the acronym. ICAO introduced the term "Extended Diversion Time Operations" (EDTO) in 2017. The European Union Aviation Safety Agency previously used the term "Long Range Operations" (LROPS) for restrictions on airliners with three or four engines.