As a little update, I tested the MP air to air with a friend the other day.
Players (from my understanding

) will have the option to play for keeps, or play for say 'training'.
We have a little gizmo in the cockpit, that when depressed, keeps your aircraft from exploding in the sky. Forget to turn it on, and you'll appear as a flaming ball of fire to the other player.
Now let's say you don't want to play for keeps, you and your friend can both use the little gizmo in the cockpit, and say I fire an AIM-9 or score a guns kill on my opponent, I have audio feedback of a confirmed hit, and can thus call knock it off.
I am not 100% sure if we are going to implement say a smoke trail after a confirmed hit (like those TOP GUN propeller flying guys have), or if we will leave it as is. I will keep you all updated.
Currently (and here to stay), you can destroy any AI aircraft using the Air to Air weapons. In the next few days, I am going to do testing with other payware aircraft, and see if I can in fact make say the Aerosoft F-16C explode in MP (nothing against Aerosoft...just testing).
Will keep you all updated, and we'll post video soon.
One thing I must say, dog fighting with the F-15E against a buddy in MP is pretty intense. You're flying the plane not on the airspeed readout in the HUD (since you're likely to be padlocked on the opponent), but on the approaching stall horn...BEEP BEEP BEEP BEEP BEEP (and when you've pulled too tight) BEEEEEEEEEEEEEEEEEEEEEEP!
It is a very...how can I say this...poopy feeling seeing your opponent closing on your six, knowing your energy is nearly depleted with the audio que of the BEEEEEEEEEEEEEEP, but damn I have never had so much fun dog fighting in FSX!
Best regards, Diego