Bah, searching for a book series. Help!?

So, I ready this series probably at least ten years ago when I was in high school. I can only remember vague details, so lets see if you guys can help! It would have been a series of 5, maybe 6 books. In the beginning its about a young man who joins the military of some sort and he becomes a scout for the group. There is something about another race that lives on the planet and I believe they have wings. I don't remember for sure but they maybe live in the sky? Seriously that's all I remember but it was a good series and I'd like to re-read. Anyone know??