Yeah I sort of wish I had put more time into the vehicles early on since I have a flight stick. The problem is the jets are sort of useless. Dice mentioned doing something to make them better but I'm not sure what they did lol.
I found that the best way to get points in a jet is to join a server with not very many people in it. If you join a 64 player server with no upgrades you'll be shot down by people on the ground instantly. It doesn't take many kills to get the flairs and homing rockets. Another way is to just find someone you know who also has the game and take turns killing each other in vehicles.
Works well with the jets.