As an outsider, I take it that the flyby was well rehearsed and practiced in a simulator beforehand(and at least authorised at management level)? Potentially, that was a very risky manoeuvre. Had it been an 'off the cuff' flyby, I too would be concerned as a fleet manager - particularly if it had other than essential crew on board.
Personally, I believe that was too low. I agree with the comment that 100' would have been more appropriate and 99% as effective.