That's a bit too much, speeds like that mean almost Mach 3, which is much, much faster than any real fighter ever got close to (SR-71 did, but it was a recon/spy plane).
IMHO, if you're going for realism, the preferable velocity for fighters would be around 300-400m/s, with AB up to 700. Of course, in space, these are still inaccurate, but then, you'd need a fully newtonian flight model to really simulate space flight. This means, for example, infnite max speed, but this also means you'll start hitting practical speed limits, not to mention the fact you'll be working with relative speeds then. In short, combat would be completely different. Unfortunately, full newtonian flight model isn't implemented in FSO yet,