Look at Flanker 2. The original game had low-res mirrors that didn't hurt FPS but also were of limited utility. When you saw nothing but sky out the front it could help you with your orientation, but that was it.
With patch 2.03 they added hi-res mirrors that you could use in combat, but the FPS in the cockpit took a big hit. Frankly, if you see a bandit in your mirror, you're already dead.
The Jedi Master