Not a new Feature, but a change to an existing feature. In 2.0, originally, it was very easy to level up in airports, but now it is progressively longer. The original version was too easy, but the newer system would discourage players from continuing. I say that the amount of XP, or whatever it is, required to level up in each airport, is proportional to each airport (IAD, LHR, MCT would require more XP than INN, BRI, SXM ect) , and for it to take slightly shorter amount of time to complete each level, meaning that all airports could be unlocked without paying within, say, a year of first playing, for a few hours every week