Wikipedia
Powerback is used by aircraft to move backwards on the ground using the power of their engines along with the aircraft's thrust reversal. In Europe only propeller aircraft tend to use powerbacks as a means of reversing, while in the United States some larger jet aircraft also perform powerbacks.
While many aircraft are physically capable of performing powerbacks, many companies impose restrictions on the practice, mainly due to the risk of foreign object damage from debris propelled into the air. Small metal objects are particularly dangerous as they can be propelled into terminal windows, employees on the ground or even the aircraft itself. Northwest Airlines' fleet of DC-9 aircraft used to commonly utilize powerback operations at certain airports, however the airline discontinued the practice in 2005 citing the need to conserve fuel.
In addition, in the United States, restrictions on powerbacks are enforced by the FAA, and the local aviation officials. Only certain gates at certain airports are approved for powerbacks, and are usually placarded as such. Many airlines impose stricter safety procedures for powerbacks, which often include disallowing a powerback under certain environmental conditions, such as rain or snow.
It is sometimes mandatory to powerback for take-off. In Grand Case Airport (official name L'Espérance Airport, French part of Saint-Martin island) the runway can be used only by ATR-42 and ATR-72 after a powerback to get its full length available.
Other places such as Lahad Datu, Sabah, Malaysia, MASWings pilots who are flying the ATR-72 occasionally employ powerback to allow them to utilize the available runway length for take off.