By 2525 numerous ships of the class were either mothballed or stripped for parts, with a number being reassigned to Naval academies across UNSC territory as training vessels.

Ships of the same class may be referred to as sister ships. For example, USS Carl Vinson is a nuclear aircraft carrier (ship type) of the Nimitz class (ship class). This is distinct from a ship type, which might reflect a similarity of tonnage or intended use. They were subsequently replaced by the Marathon-class heavy cruiser.The Halcyon-class light cruiser (Pronounced halsn) (known as Human Attack Ship classShip classA ship class is a group of ships of a similar design. The Halcyon-class entered service with the UNSC Navy during the late 2450s. The Halcyon-class light cruiser (Pronounced halsn) (known as Human Attack Ship class C-II by the Covenant) was a United Nations Space Command cruiser starship classification designed by Dr. Wartime refits conducted in 2530 upgraded the MAC to a Mark III Heavy Coil system and increased the total number of railgun batteries and missile pods to 30 and 48 respectively, also increasing the ship's PDC compliment to 100, granting increased coverage. Defensive measures include 200 centimeters of Titanium-A battleplate, electromagnetic reactive armor, and an electronic countermeasure suite. Secondary weapon systems include 20 14-inch/45 caliber railgun batteries, 26 anti-ship missile pods, 8 nuclear missiles, and 75 Butress point-defense cannons.

The primary armament of the Halcyon-class is single a Mark III Light Coil Magnetic Accelerator Cannon. The class was also equipped with a Kawanishi Engineering SED-2550X Shaw-Fujikawa Translight Engine for faster-than-light travel. The most famous example of this ship is the Pillar Of Autumn as it appears in the original Halo: Combat Evolved. This configuration provided only 10% of modern engine output as of 2552. This is a laser cut wooden model kit designed to look like the Halcyon Class Light Cruiser from the Halo series. Shipboard power is provided by a fusion reactor, with six impulse drives for sublight propulsion. The main engine assembly consists of four underpowered C2H reactors, two primary RT-5 series impulse drives and four secondary N1 series impulse drives. The class is well known for its durability, despite suffering from poor acceleration and maneuverability, a Halcyon-class can remain combat effective, even in the event of losing 90% of its armor plating. An Omega-pattern bridge module is slung underneath one of the forward sections and eight launch bays are located on the port and starboard flanks. Halcyon-class cruisers are 1,170 meters (3,838.5 feet) in length, with a superstructure composed of five hexagonal and octagonal sections mounted onto each other.

Halcyon class light cruiser