AD FAA-2011-0258

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD requires, for certain airplanes, installing two warning level indicator lights on each of the P1-3 and P3-1 instrument panels in the flight compartment. This AD also requires, for certain airplanes, replacing the existing P5-16 and P5-10 panels; and, for certain airplanes, replacing the basic P5-16 panel with a high altitude landing P5-16 panel. Additionally, this AD requires revising the airplane flight manual to remove certain requirements of previous AD actions, and to advise the flightcrew of certain changes. This AD was prompted by a design change in the cabin altitude warning system that would address the identified unsafe condition. We are issuing this AD to prevent failure of the flightcrew to recognize and react to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (a lack of oxygen in the body), and consequent loss of control of the airplane.