ETOPS
There are generally two accepted definitions
Extended Twin (engine) Operations
or
Engines Turning Or Passengers Swimming
Basically, once the reliability of an engine is proven to be of a certain standard the aircraft is allowed to fly further away from its nearest suitable diversion airfield. 120 ETOPS means 2 hours- 180 means 3 hours etc etc. The longer your ETOPS approval the further south you can fly across the Atlantic (or Pacific) nearer to your optimum Great Circle track to your destination or avoiding the eastbound jetstream. Otherwise you have to fly within 60 mins of Scotland/Iceland/Greenland/Canada. A basic definition.
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