Armada

An Armada is a good-sized unit of starships that is made up of several Task Force's.
Each Armada within a Fleet is designated with a greek letter, Alpha, Beta, Gamma, Delta, Etc.
The "lead" Task Force's flagship is also the flagship of the whole Armada and the commanding officer of that ship is also the commanding officer of the whole Armada.
The Armada is part of a larger unit known as a fleet.