See for instance this Lufthansa flight: flightradar24.com/data/flights/lh8384#2af9f823 About two hours longer flight time when avoiding Russia. Will presumably mean that the same number of flights can not be maintained with the same number of aircraft.

I mapped the direct route using gcmap.com/mapui?P=AMS-NRT. Going north creates problems with northeast Siberia and the Kamchatka Peninsula.

@StephenS note the updated answer

Should "Another option would be to go East across North America instead of West" be "Another option would be to go west across North America instead of east"?

Yes, @Pondlife, it would. :/ I'm mapping about AMS->NRT, but looking at the map I'm thinking NRT->AMS. Edited to more clearly state what I was after and to clear my confusion.

One path that avoids Russia is roughly AMS-IST-TBS-TAS-NRT (that is, via Istanbul, Tbilisi, and Tashkent). 7222 miles in gcmap (gcmap.com/mapui?P=ams-ist-tbs-tas-nrt), which is shorter than the route via Alaska. Looks pretty comparable to the Lufthansa flight illustrated.

AMS-SGN-NRT actually goes via Russian and Chinese airspace - it's a bit counterinuitive. Rerouting south, say AMS-IST-SGN-NRT, gives 9,187 miles. The westbound routes start to look good...

For the westbound route, something like AMS-OME-ATU-NRT does a better job of avoiding Kamchatka and shaves the distance down to 7,450 miles in the bargain. (Those aren't viable airports for stops, of course — I'm just using them as waypoints to get a better idea of the distance.)

"They're probably avoiding Ukrainian air space too, just to be on the safe side." You're kidding, right? I mean, there's no "probably" involved here - it's a warzone with active military aircraft shooting things on sight. Of course they're avoiding Ukrainian airspace.

The answer with a picture, +1. But it doesn't really tell me anything. Usually it would have been a parabola with most of it in Russian airspace?

This looks like AMS-NRT would be the choice. Can you expand of why it is not taken? It's probably obvious to people who are into these topics... is it the cold or the weather over the pole? Is it the significant risk of not having an airport to go down in an emergency? Or do planes just not go 5085 miles in one go due to fuel limitations?

@AnoE sounds like a good opportunity to search the site for your answers and if you don't find them, as new questions.

@J... as noted, "A quick browse of Eastern European airspace on FR24 confirms a large hole in tracked traffic over Ukraine at this time." Not sure if your comment came before/after the edit that included that, though.

@FreeMan My point was that you don't have to infer this from a radar map - there was a NOTAM posted the minute war broke out. Civil aircraft never fly over warzones. You're guessing at something that needs no guesses.

@J... It's not a "no brainer" actually... previous flare-ups around the world haven't automatically resulted in civil aviation avoiding the area... including during the previous Crimea conflict - see MH17: en.wikipedia.org/wiki/Malaysia_Airlines_Flight_17

@J... Not really... I mean, what is "full-scale war"? Neither side has declared war... Crimea conflict had planes, tanks, troops, missiles etc, too.

The russians are trying to beseige the Ukranian Capital... what here dosen't indicate a full scale war?

OK, kids, this is Aviation, not Politics or [what defines full-scale war]... let's keep it more-or-less on topic.