I enjoyed the history of ETOPS-138 [0]. ETOPS-120 leaves some small triangles of the Atlantic inaccessible, particularly if one emergency airfield is unavailable. A 15% increase to 138 minutes covers it.
Anecdotally, though, my experience as a commercial passenger feels like airlines fly almost directly over pacific islands rather than within X minutes of diversion. My memory may be anchored in bygone years.
[0] https://aviation.stackexchange.com/questions/30979/why-etops...
> pacific islands
Depending on the jet streams, the flight can take the great circle route [0] or taking advantage of the jet stream [1] and flying more southernly
[0] https://flightaware.com/live/flight/JAL6/history/20230108/02... [1] https://flightaware.com/live/flight/JAL6/history/20230105/02...
The Japan to Europe flights are even worse. The great circle route cuts west, straight across Russia [0]. These days, they fly east to the Bering Strait then more or less directly over the north pole [1] (though probably easier to see on great-circle: [2])
[0] http://www.gcmap.com/mapui?P=HND-FRA
[1] https://flightaware.com/live/flight/DLH717/history/20230109/...
Back in the Soviet era when USSR airspace was closed to most Western flights, planes couldn't do that route non stop from Europe, so had to stop over in Anchorage for refueling.
http://www.gcmap.com/mapui?P=BINP%2CFRA-KUTAL%0D%0A&MS=wls&D...
Need to find an excuse to go to Japan
Playing around, a theoretical NUE (Nuremberg) to KUTAL flight comes within 1 mile of the North Pole
Well into the 24 hour polar night/day period though (depending on time of year)
A modern 777 at most airlines for example has an ETOPS rating of 180 minutes.
That's 180 minutes of flying with a failed engine. So you have to take into account whether you can maintain altitude on 1 engine. Most of the time you can't, you'll be flying lower. Which means slower speed, so the calculation is 180 minutes at that speed.
This is accomplished by having air strips which can take massive planes like A350s at remote places which can’t justify planes of that size normally like Newfoundland, Greenland and the Azores
While these are mainly there for military and temporary emergency use, in 2001 they were used far more - with dozens of planes landing at tiny towns like Gander and St. John’s in Newfoundland, places which only really expect a single large plane to land and refuel rather than 30 with passengers to accommodate for days.