 The first (older) type IIIA is the most common, where the operator must first remove the "plug" type hatch from its frame before disposing of it on the wing (or inside on the adjacent seats).The second type is the self-disposing Type IIIB hatch, found on more modern aircraft (such as the Boeing 737 Next Generation) which has been designed to both simplify the opening of the exit and to reduce the hazard of the removed hatch blocking the exit.This is accomplished by the passengers simply pulling in and down on a handle recessed into the top of the door and initiating the exit's self-opening mechanism, whereby the door rotates up and out on a hinge at the top of the exit frame.