All planes catapulted upward and explode after flight leader dies

[genericpilot]

Not sure whats going on but after 17 completed missions on a kursk campaign this has happened. Victory conditions have also been set to none

[Lowengrin]

Generally when all the planes first spawn and they catapult, it means that their takeoff coordinates are corrupt.  I suspect one or more of your campaign data files got messed up.  Under the Edit menu, you can try the "Restore From Last Mission" option and see if that repairs it.