Wingover( Monster Manual V, p. 205)
You change direction quickly once per round while airborne.
Ability to fly,
This feat allows you to turn at an angle of up to 180 degrees in addition to any other turns you are normally allowed, regardless of your maneuverability. You cannot gain altitude during the round you execute a wingover, but you can dive. For more information, see Tactical Aerial Movement in Chapter 3 of the DUNGEON MASTER'S Guide.