Ok, most of us agree that a push in mid-air is a PC foul, even if the defender gets there late.
How about if A1 jumps into the air with a straight arm and dosen't move his arm at all, ala' The Heisman trophy, and then crashes into B1 who has got there late?
Does this fit MTD's response about arms having to go with the body?
A1 didn't "push" off...he stayed in the same pose throughout the jump. This is really going to look bad calling it a block, because the hand/arm of A1 is in a straight arm position...but MTD may have something with this one, because the hand/arm did follow A1 with no "pushing" going on...it was a straight arm...not a push.
Just stirring the pot a little.