Hmm.. I haven't seemed to have that problem. I flew amongs 4-17s in a fighter, and they all had their guns firing, had no freezups during flyby, and I've also been in a 17 formation and have had no frame rate problems.
Celery 464, 128M Ram, TNT2 Ultra (32M). Res: 1024x768 32Bit color. Running Hires texture pack, and the most it dropped during those flights was from 38-44 down to 32-35
Still very playable for me.