N977HS is taken. It's currently assigned to a 2012 Gulfstream Aerospace GV-SP (G550) registered in Xxx, OK.
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.
N977HS has been worn before. Past registrations from FAA deregistration records:
Tails one nudge away from N977HS that aren't assigned or reserved: