From Halopedia, the Halo wiki
Marine Tiltrotor Operational Test and Evaluation Squadron Twenty-Two (VMX-22) was a tiltrotor squadron in the UNSC Marine Corps originally set to appear in Halo: Reach. The squadron would have operated the UH-144 Falcon tiltrotor aircraft, as indicated by markings identifying the unit in early models of the craft.
The squadron would ostensibly have derived its lineage from the unit of the same name in the United States Marine Corps. Established in August 2003 at Marine Corps Air Station New River, this squadron was responsible for testing the MV-22B Osprey multi-mission tiltrotor aircraft, and all future aircraft of the type. Although Falcons emblazoned with the VMX-22 markings are not featured in the final version of Halo: Reach, several other real-world units make an appearance.