Hi Gosd,
try deleting the uisel file located in the application data folder.
The other thing is to make sure the flight type is set to free flight, or if on dog fight or intercept etc make sure the enemy aircraft selection box's are populated with a plane type. I've found sometimes when changing era's that the airbase selection box does not have a valid airbase selected (not all era's have the same airfield locations) and aircraft selection box's are empty, and if you try to start a flight he game CTD. populating the fields with an airfield and aircraft fix's that.
HTH's
regards Rob.