LGA/DCA Perimeter Rules
Not sure if these are part of the game already, but they would be added to political restrictions. Basically, LGA has a rule stating that no flights longer than 1500 miles can use the airport, while DCA's is 1250. While I understand that there are real-life exceptions, I feel like it'd be best to implement both into the game (especially LGA's, which I don't believe I've ever seen an exception for).