A small graphics bug:
I was testing my computer's stability in AH and loaded up a P-51D with full fuel and let it fly on autopilot. A few hours later, the cockpit, plane, gun tracers, and ground (water) disappeared. I thought it might be a problem due to the high altitude it had reached, although without the cockpit or plane visible I couldn't determine how high I was. Firing the guns showed no tracers.
The clipboard would come up normally.
I started a descent and thought I'd descend until I could see the water, but I impacted the invisible terrain before the terrain became visible again.
After getting back to the tower, I re-upped and everything worked fine so my guess is that if you get too far from the map, not only does the terrain quit drawing, but anything related to the plane quits drawing as well.
I wonder if the art for the plane and the tracers were floating somewhere at the boundary of the drawing box, but this sort of sounds like a bug that could be exploited if a boundary was exceeded allowing me to fly around without the cockpit and aircraft art.