He's quite the avid hunter, so I'm sure he'll go in armed. I'm most concerned about the time after he lands and before he gets back to the plane. The potential for trouble is obvious.
I think he needs someone to stay with the plane. If he hasn't already gone and this is a weekend rescue, I think I'll volunteer to go with him. I'll guard the plane while he gets his FIL. A few shotgun blasts should be all that's needed to discourage a hijacking from occurring.
God be with you and I hope it is a very fruitful mission.