The proposed irective, however, will not require the sweeping insulation replacement that the agency had discussed back in October, shortly after a SwissAir plane crashed off Nova Scotia following a report of smoke in the cockpit.
FAA officials said that the agency backed off the plan, under which it would have ordered the replacement of insulation in nearly every U.S. commercial airplane, because recent research showed that most existing insulation passes or only narrowly fails the new flame test.
Instead, the more limited order will apply to about 700 U.S. airplanes built by the former McDonnell Douglas Corp., which is now owned by the Boeing Co. They include the MD-80, MD-88, MD-90, DC-10 and the MD-11, which is the type of Swissair plane that crashed last September, killing all 229 aboard.
Under the proposed order, airlines will have four years to replace all metalized mylar insulation with products that pass the new flame test. The order will take effect after a 45-day comment period and time for revisions.
Those carriers primarily affected are American Airlines, Continental, Delta and TWA, although Alaska Airlines, FedEx, Reno Air and US Airways fly some planes covered by the order.
In 1997, McDonnell Douglas told airlines they should consider replacing metalized mylar insulation because it might be flammable. Insulation is used in airplanes to keep passengers warm and to dampen the noise of rushing air and engines. It is often installed in sheets, much like attic insulation.
Since the SwissAir crash, experiments the FAA has conducted confirmed concerns about metalized mylar aired by both McDonnell Douglas and Boeing.
"It doesn't just fail the test; it fails it by a wide margin," Beth Erickson, director of the FAA's aircraft certification service, said in an interview. "If there is a low-level ignition source, like an [electrical] arc, it will catch on fire."
While some other materials do not pass the new test, "they miss it by a much narrower margin. Therefore, they don't pose a safety threat," Erickson said.