The creature can attack on the wing.
Prerequisite: Fly speed.
Benefit: When flying, the creature can take a move action (including a dive) and another standard action at any point during the move. The creature cannot take a second move action during a round when it makes a flyby attack.
Normal: Without this feat, the creature takes a standard action either before or after its move.
Source: Monster Manual (version 3.5), page 303.