At the Rise of Nations Heaven Forum, Rohag posted this tidbit about airbases.

When you build planes (fighters/bombers) at an airfield they remain inside the airfield until you give orders. You have your choice of issuing orders to individual aircraft assigned to an airbase or to the airbase as a whole – in fact, you can give orders to the airbase even before the construction of any aircraft and they will go to the spot or on the assigned mission once they are created. One tricky thing is the “repeat orders” stance button for airbases; you’ll find it in the options box in the lower left of the user interface – the default is ‘on’ and can be toggled ‘on/off.’ While ‘on’ the aircraft to which it applies (individual or base group) will automatically return time and again to the mission or spot to which you’ve ordered it after each refueling. For a poor micromanager like me, ‘on’ is good. ‘Off’ makes the aircraft perform the one mission and then it's back for refueling and waiting on your next orders.

Useful info. Be sure to read his entire post.

I must add that I have gone from making mostly helicopters, to now making fighters. Helicopters were weakened in patch 3, while fighters are more difficult for ground troops to handle. Also, fighters tear up helos, so if your enemy makes helos, you'll want fighters, and if they make bombers, you'll want fighters, and if they make fighters, you'll want more fighters. Looks like a dominant strategy to me. So just make fighters first! Also, most people don't make enough mobile air defense (whereas the AI makes too much).
posted by Tim at 9:10 PM