There 'aint nothin' much bigger than .45 cal. They certainly won't have .50 cal Desert Eagles! .45 is a huge slug--and most .45 pistols would be inappropriate for use by minimally trained pilots. Also, "sub-sonic" does not automatically include or exclude Glaser-type ammo-- the type of slug (pre-fragmented, like glazer, etc.) usually operate at sub-sonic speeds-- but don't have to. I'm sure the ammo will be specifically picked for minimum penetration-- so probably sub-sonic, probably .40 calibre.