Very easy and quick achievement.
You can do this on Level 1, on any difficulty in Campaign at any speed.
A little ways into the level, the game will prompt you to pick either the left side of the screen (fly straight), or the right side of the screen (free flight). Simply stay on the right side of the screen until the game picks up again. This "path" enables you to fly in any direction, eventually the path will end and you will continue to the end of the level. The achievement will pop upon completion of the current level.