I am not quite sure what you mean, and I don't know what Behaviour you are using (Bullet?), but perhaps you could try the following action:
Event - Plane hits edge of layout
-- Action - PLANE: Set Mirrored
-- Action - PLANE:BULLET: Set Bullet angle of motion 0, or 180, depending on which direction you want it to go next.
If the plane is only travelling Left or Right then he can be Mirrored. You might need to disable "Set Angle" on the Object under the Bullet behaviour settings otherwise it will always set the animation to the angle of motion. If you aren't using the Bullet behaviour then Mirroring should work fine without any other adjustments.