Very good response. I’d like to add that if you are talking about 1 TR (unsupported) vs. 1 TR (also unsupported), the defender will always win since the attacker has 0 attack value. I.E. essentially you can’t do it.
Unless you play with an always active AA gun, flyovers on AA guns on the Non Combat Move cannot be fired upon by the AA gun.
In any attack of the nature you described, the AA gun must roll one die for each attacking plane (that is, FTRs & BMRs) at the same time–attacker chooses losses. This concept is reflected throughout the game in various different instances. For instance, your dice in Combat are rolled by “column” on the BattleBoard. After you roll for all “columns” then count the raw # of hits, the opponent chooses what got hit (except in the rare case when multi-national defenders cannot agree, in which case the attacker chooses). In research as well, you can’t buy 1 Tech Die at a time and roll till you get a hit; you must decide how many dice you want and roll all of them at once.