Airworthiness Directives; Boeing Model 777 Airplanes

We are adopting a new airworthiness directive (AD) for certain Boeing Model 777 airplanes. This AD requires an inspection to determine the manufacturer and manufacture date of the oxygen masks in the center and outboard passenger service units, crew rests, and lavatory and flight attendant oxygen boxes, as applicable. This AD also requires related investigative/corrective actions if necessary. This AD results from a report that several passenger masks with broken in-line flow indicators were found following a mask deployment. We are issuing this AD to prevent the in-line flow indicators of the passenger oxygen masks from fracturing and separating, which could inhibit oxygen flow to the masks and consequently result in exposure of the passengers and cabin attendants to hypoxia following a depressurization event.