Hangar C-01 is a generic United Nations Space Command term for one of the two-deck Pelican hangers below the MAC gun on an Orbital Defense Platform.
Cairo Station Hanger C-01
During the First Battle of Earth, SPARTAN-117 was able to take the Covenant bomb from Firing Control by wresting it from the hands of its Elite and Grunt guards, move it to Hangar C-01, and then activate the airlock door, explosively decompressing the bay. The SPARTAN-II was miraculously able to guide his trajectory to intersect with the damaged engine of a nearby unshielded Covenant Assault Carrier. He then drifted away to UNSC In Amber Clad and detonated it, destroying the heavy warship.