Flight Barrier

Regarding the barrier in flights. I encounter it in strictly defined places on the map, and it often forms part of some larger structure (something akin to a dome, a transparent partition several meters above the ground, invisible from the earth, and so on). Incidentally, I once managed to emerge beyond the confines of such a transparent dome, and was immediately informed that I had died :). As for the map, this area is in the northwest. The dome appears slightly north of the city, while structures resembling transparent walls above the ground are found slightly to the west. Unrestricted high-altitude flights are possible in the south and southwest of the map, frequently near a castle. Occasionally, they manifest at the very edge of the northwest corner. In that region, I find eternal snows, a dark sea/lake bordered by high mountains. These are my observations.