From Halopedia, the Halo wiki
The Unidentified human transport ship is a human transport ship in use by the UNSC and Insurrectionists.
In January 2553, Insurrectionists of the New Colonial Alliance boarded UNSC Infinity using this ship.[1] The United Rebel Front had acquired this ship for use on the moon of Talitsa.[2]
The Outcast ship taking off.
The transport ship heading towards UNSC Infinity in Halo: Escalation.