N592 is taken. It's currently assigned to a 1981 Sell Gilbert A CASSUTT IIIM registered in Conroe, TX.
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.
Tails one nudge away from N592 that aren't assigned or reserved: