Troop deployment pod
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The troop deployment pod is an extension attached to a D77-TC Pelican's overhang to increase its passenger load capacity featured in early Halo: Combat Evolved concept art for the Pelican. One iteration by Marcus Lehto had a carriage inserted onto the back of the craft to make the "blood tray" larger.
While not seen or directly mentioned in the series, the fact that Pelicans sometimes carry unusually large complements of people in the novels may suggest that the UNSC use some form of troop bay extension. At the end of the Battle of Sigma Octanus IV, the Spartan-IIs were able to evacuate a group of surviving civilians as well as Corporal Harland's squad and the remaining Marines from Alpha Headquarters. Including the SPARTANs, this would make a total of forty-six people, which a normal Pelican cannot ferry. It was also once implied that a Pelican with a troop bay extension was used to ferry the seventy-five SPARTAN-II candidates; however, the 2010 reprint of Halo: The Fall of Reach, Halo: Fall of Reach - Boot Camp and Halo: The Fall of Reach - The Animated Series retconned this Pelican into being an Albatross.