Action Replay Codes for Aerobiz Supersonic

You can use 7E25F800 which tells the game you have no regional routes anywhere, you then create your route(s) and then turn the code off. Note that you will not be able to see the route lines on the map, but the routes are there, you will even see you have 42+ cities, or 41+ routes, plus gain all the passengers and profits.

Inter-regional route code is 7E25F700, same thing as above, just for turning off the regional connecting flights count.

To give cities an immediate maximum available slots of 255 (you still have to negotiate for your own available amount):
Tokyo = 7E3EEDFF
New York = 7E3F03FF
London = 7E3ED5FF