I purchased it in May of 2010.
May 2010, are you sure it's KDFW ? It was released in early August 2010. However, if you bought it at the release date, then yes, we had several updates, and one dealt with the altitude.
Are there any updates? If so, I can't seem to find them on the FSD website.
On the top of this forum:http://www.fsdreamteam.com/forum/index.php?topic=3391.0