The Cariburn doesn't have forward-swept wings though - it has a delta-wing. TBH, it doesn't matter what it is. It's not like we can capture it, or even if we'll know who it belongs to. If the mysterious 'they' are attacking us in the middle of an exercise, I imagine they're not boldly showing off their insignia and serial numbers. And if we do need to find out, we'll know at the appropriate time.