N728C is taken. It's currently assigned to a 1957 North American T-28C registered in Leesburg, VA.
See the full aircraft record →A tail number only frees up if the owner deregisters the aircraft or moves it to a different N-number — and even then the FAA holds it before releasing it to the public.
N728C has been worn before. Past registrations from FAA deregistration records:
Tails one nudge away from N728C that aren't assigned or reserved: