The window heaters have been tied to dozens of incidents involving in-flight fires, smoke, open streams of electricity known as electrical arcing, and shattered windshields in Boeing planes. In many cases, pilots have made emergency landings.
The source of the problem was identified in 2004 as a simple loose screw that chafes power wires where they connect to heating wires in the windows.
The most recent incident was an emergency landing by a United Airlines Boeing 757 at Dulles International Airport in Virginia on May 16. A fire broke out near the captain's side of the window during the New York-to-Los Angeles flight. Pilots used a fire extinguisher to put out the flames, but they had to send for a second extinguisher after the fire reignited. The fire also shattered part of the window. Afterward, passengers said smoke had drifted from the cockpit into the cabin, and fire trucks, ambulances and other rescue equipment was waiting for the plane when it landed.
NTSB has been prodding FAA since 2004 to order airlines to replace cockpit windows on Boeing models in which incidents have occurred with a new window design that uses pins instead of screws. NTSB Chairperson Deborah Hersman told The Associated Press last month that she was concerned the problem would lead to an accident.
The safety order, which FAA said will be published in the Federal Register on Tuesday, applies to some Boeing 757, 767 and 777 models. NTSB had urged that 747 planes also be included. FAA said it is considering a separate order for 747s, but didn't indicate when that might be.
The order also doesn't go as far as NTSB has recommended. Instead of requiring that all windows be replaced, the order tells airlines that beginning on Aug. 17 they must inspect planes within 500 flight hours and, if evidence of damage is found, replace the windows. The order gives airlines a choice of installing windows of a similar design or the new design. Carriers that choose old design replacements must continue to inspect windows at regular intervals.
NTSB had urged that only the new designs be used for replacements.
FAA said it was aware of 11 cases of fires in the planes over the past 20 years. However, Boeing has said it is aware of 29 incidents involving fire or smoke over the past eight years.