Which preposition to use with underbody

of Occurrences 2%

He saw rows of lighted windows, each cased in shining metal; a V-pointed pilot-housethe same where the still figure had dropped over the sill of the open windowa high-raised rudder of artful curve, vast as the broadside of a barn; railed galleries running along the underbody of the fuselage, between the floats and far aft of them.

Which preposition to use with  underbody