The last 100 longhaul flights I took, all had a screen with a map and current position.
You can ask a FA to ask the pilot, they usually do it gladly.
Flying say from HEL to HKG will be over the northpole, where in the winter you don't have a day, and in the summer no night.
You might want to have very strong sunglasses, to look from the window to the sun, and catch a maariv, for the 10 minutes or so where the sun is under (not dark), and start shacharis after that.
Once again, a pilot might be able to help with it.
Problematic are also the dateline* as there is a machloikes on where it it.
* the halachic dateline hasn't got anything to do with the regular dateline, which got decided that it start at '0' from Greenwich, UK. A while ago it was in Paris.
Some hold it to be on the east coast of China, meaning stepping into the sea in China puts you in another day.
Others hold that the dateline is on american samoa.
Someone leaving early afternoon on sunday to fly to australia, (or late afternoon/evening to japan), have according to some poskim been flying a while on shabbos.
That would require you to make havdolo.
There are other poskim that hold that you can have maximum one shabbos per 7 days.
Another problem would be that if NOT flying leDvar mitsve, you cannot commence a travel after wednesday which won't arrive before shabbos.