One of the biggest things that the airforce is well known for is recon, Cargo shipments, and some serious Bombardments.  I was driving threw my base one day and saw one of the airforces' big liner jets.  not even two of our fighters combined can match the size of one of the 4 Engines to that F***er!  The thing dwarfed our airport pretty bad.  Looked like something like an empirial palace with wings and a bad paint job.  I think the Airforce may either be completely dead in the Halo-verse, but it could also be in with those recon space-stations....  Just a thought of a possibility....    But I think the're dead. 

  Another possibility is that they went into Naval Engineering with warships and fighters...  The longsword does look kinda like the stealth bomber.   ....sorta