Section 1 contains the radar antenna behind a fiberglass-honeycomb fairing, hinged at the top. Aft of the pressure bulkhead, above the floor, are the flight deck and forward entry and galley doors. Below the floor are the nose gear wheel well, forward airstair and its door, and the electronic equipment bay. This section has two lower access doors.
Section 2 contains the passenger cabin, with windows between the frames, and the forward cargo compartment, with a door on the right side.
Section 3 contains the center and aft portions of the passenger cabin with windows between the frames, two overwing escape hatches and aft entry and galley doors. The 737-400 has four overwing escape hatches. The space below the floor includes the wing center section (fuel tank), air-conditioning bays, wheel well, hydraulic bay and aft cargo compartment with a door on the right side. This section terminates at the aft pressure bulkhead.
Section 4 contains the auxiliary power unit (APU) and horizontal stabilizer truss. Access to this section is through a door on the left side, aft of which is the APU access door and APU exhaust.