Fleet (Earth-5875)

A fleet is a large formation of warships, which is controlled by one leader among thousands of personnel. The equivalent to a smaller fleet is a battle group.

UNSC
The UNSC has massive fleet divisions under the UNSC Navy, which consists of numerous warships, such frigates and destroyers, that escort larger capital ships. Both fleets and battle groups feature one covert prowler to act as the "eyes and ears" of the formation, as well as hidden saboteurs.

Covenant
The Covenant Armada possessed fleets of thousands, with ships much larger and much powerful than those of the UNSC. Frigates were a common occurrence among fleets, while cruisers and destroyers were mostly relegated for glassing operations. As with the Armada's organization, each fleet is its own self-sustaining force, being capable of operation without any supplies for large periods of time duo to their DSC-class support ships and huragok contingents. The most common fleet warships were the CCS-class battlecruisers under CAS-class assault carriers.

Trivia

 * Naval fleet at Wikipedia.