Denver Broncos owner Pat Bowlen owns a Citation X N978DB
The aircraft seems to fly as OPT978 as indicated above, but also sometimes as N978DB. The aircraft is likely managed by Flight Options, and likely flies as an Options flight (OPT978) when under charter to customers other than the owner, and as N978DB when the owner is on board. (This is a guess based on my own experiences in that industry).
I saw this aircraft arrive at KAPA recently and was surprised to see N978DB arrive when I had expected a normal Options CX. The plane has winglets now as well!