The Adrenaline Vault: Fly!

Review by Adam Swiderski. "This is one advanced, playably deep simulation on the piloting of civilian aircraft."
http://www.avault.com/reviews/review_temp.asp?game=fly&page=1

Maximum3d.com: Fly!

Reviewed by Scott Meyers. "I would highly recommend this game to someone learning to fly, as the instrument flying is second to none."
http://www.maximum3d.com/reviews/fly.htm

FLY! II

Official site. Offers program information, knowledge base, FAQs, downloads, screenshots, product support, and links.
http://fly.godgames.com/