This sometimes happens in games, usually for me in Battleifelds game, where methinks the PC gets so busy with GFX, effects and sounds, that it forgets to, or cannot continue with plotting and moving the A/C, think of it like a un-crash to desktop crash.
Could be related to virtual memory, memory leaks, too high a setting for some hardware or too many programs running in the background perhaps. Myself, I might have had something similar happen in IL2 once or twice since the game came out.
There should be someone who cold better advise you at SAS1946, 1CForums or other (of your national language) IL2 related forums.