The AF could take the option of simply joining with the Navy in the procurement of the system, if it satifies their needs.  If the AF intends, or needs, to substaintially modify the system for their requirements, then they may chose to create their own Progeram of Reord.  If the AF chooses to partner with the Navy, then they could simply have an "Air Force version" and a "Navy verison".  These are just options and not requirements.  As noted in Acquipedia article regarding Program of Record https://www.dau.edu/acquipedia/pages/articledetails.aspx#!522 , the Army is only serivce that has a specific policy for these types of actions.  Therefore, it is possible for the AF to agree to either of the aforementioned approaches.  The respective Milestone Desicion Authority (or higher depending on the circumstances) will have to agree to whichever course of action is chosen.  It is recommended the decision be reecorded in an approriate Acquisition Decion Memornadum (ADM) as the service directs.