again...jump shooter jumps into defense

[zanzibar]

Thanks for everyone's responses on this topic. I'm still trying to clarify the rules that apply to this play. I was searching the books today trying to support a decision on this topic.
Situation: B1 goes airborne to defend a possible shot by A1. B1 leaves the ground first and A1 fakes a shot. After B1 is airborne A1 jumps into B1. In the ref's judgment no contact would have occurred if A1 does not jump in.

This is my opinion and why I would rule this way:

1. Once B1 goes into the air A1 has to allow him to land unless A1 was in this space before B1 became airborne. I know A1 has the ball and is a shooter, but I don't think it has any bearing on this play.
2. 4-19-1 says... it is a player foul which involves illegal contact with an opponent which hinders an opponent from performing normal defensive movements.

I think most of the time this play would be a no call.
I don't think it makes a difference whether A1 jumps forward or sideways.
Comments..... Agree or disagree?