From Halopedia, the Halo wiki
The G81 Heavy Gunship, also known as the G81 Condor is a custom heavy gunship variant of the D81-LRT Condor dropship employed by the stranded UNSC Spirit of Fire during the Second Ark Conflict. It was created by Isabel.
The AC-220 Vulture is still currently “officially” the heaviest standard combat air unit the UNSC has to offer, though there is nothing official about the Condor Gunship. Described as a flying fortress, the G81 Condor is slow-moving but extremely powerful. Although it breaks a several UNSC weapons platform and safety regulations, this does not impact its impressive combat performance.
The Condor gunship's armament consists of five twin pulse lasers, whose high rate-of-fire and ability to independently target enemy units makes them ideal against massed opponents. A Ballista mini-MAC turret is also fitted, whose power allows it to defeat heavy targets. It can be upgraded to fire three shots in rapid secession. The weapon systems are powered by older capacitor banks which replace the slipspace drive, which also removes its faster-than-light capabilities.
Condor gunships were created in 2559 during the Second Ark Conflict. The AI Isabel modified several civilian D81-LRT airframes to provide heavy air support for the ground forces of the Spirit. It was first employed during the Banished attack on the control room of Installation 09.  One of the G81s employed by Spirit of Fire were destroyed by Forerunner defenses during Operation: SPEARBREAKER, in an attempt to stop a Forerunner Despair-class fighter from being launched by the Banished.
Halo Wars 2
The G81 Condor can be built by all UNSC leaders at the Firebase. As the Super Unit for UNSC, it is able to take on both Banished Scarabs and Retriever Sentinels. It is effective against vehicles, aircraft, and structures, but is only okay against infantry. In Blitz, the Condor costs 300 energy, and is only on the field for 60 seconds.
List of appearances