score:5
Flying on the last day of your visa can lead to complications but as this answer outlines, you should be good -- nonetheless, you will need to do some extra paperwork if your flight is cancelled or delayed.
The air space doesn't matter for visa purposes, so much so it is entirely possible your flight enters Schengen airspace without landing there, here is an example of a flight between two non-EU airports crossing Schengen airspace: