If you fly in a straight line, you can gain altitude in flight more easily than others.
Prerequisites: Str 15, fly speed (average or good maneuverability).
Benefit: When flying, you can gain altitude and still move your full speed provided you fly in a straight line.
Normal: Without this feat, you must move at half speed to gain altitude (see Tactical Aerial Movement).
Note: Creatures with a fly speed with perfect maneuverability do not need this feat as they already gain altitude without the half speed penalty.
Source: Draconomicon, page 72.