File Pilots and flights attendants attend a memorial service on the beach after the Swissair Flight 111 crash.

By Michael Tutton / The Canadian Press

Aviation regulators in the United States will give airlines an extra year to remove insulation blankets suspected of playing a role in the crash of Swissair Flight 111.

In August 1999 the Federal Aviation Authority - reacting to recommendations from Canadian investigators of the Swissair crash - proposed to give airlines four years to remove the metalized mylar material.

But on Friday it issued a final ruling allowing carriers five years to remove the insulation, saying it is a possible fire hazard.

Swissair Flight 111, an MD-11, was insulated with metalized mylar when it crashed off the coast of Nova Scotia on Sept. 2, 1998, killing all 229 people aboard.

Although the cause of the crash has not yet been pinpointed, investigators say there may have been an electrical fire near the cockpit that spread through the insulation.

The FAA said it's giving airlines extra time because it wants to avoid damage to wiring while thousands of square metres of the insulation are stripped out.

"We based our decision on safety concerns," Alison Duquette, an spokesperson for the American regulator, said in an interview.

"The most important thing to us is that . . . there are no unintended consequences. We think this is the fastest this can be done safely."

The FAA made its decision after observing the difficulties American Airlines and Swissair encountered while removing metalized mylar last year.

The insulation blankets were designed to keep heat in and noise out.

The order applies to MD-80, MD-88, MD-90, DC-10 and MD-11 planes designed by McDonnell Douglas, which Boeing bought in 1997.

Air Canada and Canadian Airlines do not fly any of these aircraft. However, the FAA ruling affects 719 U.S.-registered aircraft operated by 14 major U.S. airlines.

McDonnell Douglas told operators in 1997 they should stop using metalized mylar. There was a limited response from airlines, primarily because of the cost - estimated at between $380,000 US and $880,000 US per aircraft.

Duquette said people flying on aircraft with the insulation shouldn't be worried because the risk of fire is very low.

"We're raising the bar on safety," she said.

"This isn't material which will itself propogate a fire. You have to have an ignition source and the risk of fire aboard an aircraft is very low."

The mylar insulation was cited as a major factor in at least five other aircraft fires. It was criticized as early as 1996 by Chinese aviation authorities.

The Chinese Aviation Administration warned the FAA in 1996 of problems with the mylar insulation, urging the regulator and Boeing to "make prompt and positive response."

The FAA responded by saying it was researching the issue.

Last year, the FAA recommended mylar insulation be removed after the Transportation Safety Board of Canada said use of the blankets should be reduced or eliminated based on wreckage from Flight 111.