I would agree with you Kirby.

What if this same B player jumped straight up at the 2yd. line, made the interception, and before he could make contact with the ground, an A player pushed him over the GL into the endzone, and there he first made contact with the ground and then the ball became dead?

Would you still have a touchback? Would you have B's ball first down at the 2?

GH

Kirby, you're right. Touchback. The key here is for momentum, the player must first establish himself on the field of play. Since he is airborne all the way until he lands in the endzone, he never established himself in the field of play.

Now for Grey Hare's example. Off the top of my head, I would say go with the two yard line. Kind of like forward progress. I will have to get to the books and check it out though.

I've got B's foward progress stopped at the B2. That's where he's getting the ball.