Originally Posted by SAT Lawyer
It can do either.
AA used to power back their MD-80s (DC-9-80s) fairly frequently. But there are dangers to backing up without the use of a rear-view mirror, in addition to the possibility of sucking debris into an engine.
It isn't terribly dangerous, because you use wing spotters (don't know what they are called). One on each wing, with those little things they wave around.