Its a very different system to the ones I've used before.
Where they involve predictive movement or initiative sequences they all leave a fair degree of control over the to the player (I pick whether I shoot or not after I manoeuvre my plane, and I know the range of movement of my opponent)
Bag the Hun steps away from this – the option to shoot is available only when the chit comes up, if that means you're target has moved away, or that you haven't moved into posiiton yet, then that's what it means. Of course you don't have to shoot but it can be frustrating to find yourself sneaking up for a rear deflection only to see the target skid across the sky
On the plus side it makes tailing very powerful as that means, once you achieve it, you'll always be in position to fill the target with lead as desired.
The bonus moves took a little getting used to, one or two players thought that moving up to three times (own card, formation card, altitude card) was over-egging it and we may try it out with a bonus d4 move instead.
This and multiple dice for combat are features I recognise from IABSM as well, the combat mechanic emphasises the importance of conserving ammo and not taking long range shots at small agile targets – thats a very good way to burn off your ammo for no effect. It also helps you to really punish big lumbering targets when you get in close and personal.
I'm looking forward to more BTH style games :-)