A1 jumps for a shot,B1 jumps to block, has hand on the ball, on the way down hand comes off ball, A1 drops ball to floor, jump ball, or can A1 recover, if so can he start a dribble?

I would have blown my whistle and called a held ball while they were both still in the air (before hand came off ball).
It sounds like B1's hand on the ball prevented A1's release of the attempted shot. Thus...a held ball situation.

If B actually stopped release (had the ball hard enough, long enough - a judgement) ===> Jump
If ball was only touched and voluntarily dropped ===> Travel, due to beyond prescribed limits, or Illegal Dribble, due to beginning dribble with pivot off the floor.

Fed probably just calls it a "violation", and then we choose the signal.
mick

ok, just wasn't sure if you had to wait till player returned to floor, thanks