When trying to file a flight plan, I get said message. I'm in the US so the transition levels should be 180, and I tried typing 18000, too. I don't know what to do, if I'm missing something, or if it is indeed a bug - which I suspect.
Edit: Okay, that error message stopped,but now it says "departure and arrival airports should not be filed in flight plan". I mean, seriously? Between this and X-Plane's crap ATC, it makes me miss FSX (not that their's is amazing, but it works). I still prefer X-Plane because everything else is better, but it's like let's fucking go, how can they make the whole damn simulation that good but they don't give a shit about ATC to the point that I'm here trying this, which isn't working either?