Like I wrote here (Problems playing the game? Players ask - players answer - #43 by foxxygaucho), I’ve got the same problem, even with small(!) airplanes. No chance, to get these flight offers out of the list (only If I terminate the airline contract 
)
This issue I’ve got also since ~1 week, the time before I’ve got no problems with it. I believe, it’s a bug came in with the last small update.
Flights with a destination outside Schengen area are international.
Declare also some medium stands as international. That’s realistic. If you builded a french airport, you have e.g. in CDG medium sized airplanes to Turkey, North Africa, Serbia, Croatia, …