UNSC Point of No Return

From Halopedia, the Halo wiki

The UNSC Point of No Return was one of the most advanced and secret ships ever built by the UNSC's Office of Naval Intelligence, classified as a Stealth Prowler.

Though technically a prowler, the Point of No Return was the largest one ever built, easily the size of a UNSC Destroyer. Constructed in parts and then assembled in deep space, the ship was completely radar invisible, and when her baffled engines ran below 30 percent she was as dark as interstellar space.

Point of No Return was the wartime command and control platform for ONI section three. She was highly classified, technically she didn't even exist. Very few had actually seen the ship, only a handful had ever been aboard, and less than twenty officers had access to its most sensitive areas.

In 2531, Colonel James Ackerson met here with Captain Gibson, Rear Admiral Rich, and Vice Admiral Margaret O. Parangosky to discuss the Spartan-II project. They decided to grant Ackerson permission to begin the Spartan-III project. It was the ship that later picked up Spartan-051 after he had been "killed" in action in the Groombridge 34 System.

In 2537, Admirals Rich and Parangosky then met with Spartan-051 and Senior Chief Petty Officer Franklin Mendez again to inform him that the first 300 Spartan-IIIs of Alpha Company had been killed and to go ahead and begin training Beta Company.