This is maybe not a "personal accessory," more like a piece of art, but if your guy really has aviation fuel in his veins, he would appreciate something from the Boeing Custom Hangar collection.

These are items crafted from pieces of decommissioned Boeing commercial jetliners. You can get a 747 window frame signed by Joe Sutter, parts of 727 cockpit panels refashioned into bookends, etc. Genuine aviation history, that your BF is about to become part of.

http://www.boeingstore.com/Custom-Hangar/b/5526025011