The AIB is the Admiralty Interview Board, held in Gosport, Hants. 3-4 days of testing akin to the OASC. I've sat and passed both but failed the final selection for the RAF i've now got Navy Pilot starting Sept. So if u want some indepth info on both you can private email me. I would advise you NOT to go ground branch and then transfer to aircrew later. They invest £££ in your future as a ATC, Flt ops etc... It's a risk mate.....look about! Even Civvy if u have the capital.