[just another ref]

Originally Posted by BillyMac

When an airborne player keeps control of an attempted shot that is blocked and is unable to release the ball and returns to the floor with it, that player has not traveled; it is a held ball. If, in this situation, the shooter releases the ball, then this is simply a blocked shot and play continues. When an airborne player tries for goal, sees that the try will be blocked, purposely drops the ball, and picks up the ball after it hits the floor, that player has traveled by starting a dribble with the pivot foot off the floor, whether, or not, the defensive player touches the ball in the block attempt.

If the defender does touch the ball, it is sometimes a fine line to draw whether the drop was on purpose or not. Also, it is not uncommon to see a travel called when the defender's touch actually knocks the ball loose, but the shooter catches it on the way down.