recommended yesterday that the insulation on almost all of the

world's 12,000 passenger jets be replaced as soon as possible,

because new tests are likely to find that it can catch fire when exposed to high heat.

Some aviation officials estimated the price tag for the switch could

total billions of dollars. The recommendation grew out of the

investigation of Swissair Flight 111, which crashed off the coast of

Nova Scotia last month. While the cause of the crash is not known,

there are indications that some of the wreckage had been subjected

to heat and possibly a fire. The pilots reported smoke in the cockpit

before the crash, and "heat-distressed" wreckage from the cockpit has been found.

The retrofit, which the FAA said it will likely make mandatory after

new flammability tests and specifications are developed in about six

months, affects almost all airliners manufactured by Boeing, Airbus

Industrie, McDonnell Douglas and Fokker. Officials said the

Lockheed L-1011 - about 200 of which are still flying - appears to

be the only jet manufactured with acceptable insulation. The

material under scrutiny is not wiring insulation but, rather, looks

similar to home insulation and is used for the same purposes: to minimize noise and

trap heat. The action is not expected to disrupt flight schedules, because it

would be performed during regular major maintenance periods.

Aviation-industry officials point out that insulation fires have been extremely rare.

FAA Administrator Jane Garvey said in an interview that the

agency does not consider the fire threat serious enough to issue an

"airworthiness directive" ordering immediate replacement, but the

FAA may change its position if further research proves the threat to

be greater than expected. For now, the agency, which had

previously certified the material as not flammable, recommends

replacement at "any reasonable maintenance opportunity."

The FAA has known about the potential flammability of jet

insulation for at least two years and, possibly, longer.

In 1996, the Civil Aviation Administration of China strongly

recommended new tests after a Chinese Eastern MD-11 fire in

Beijing in 1995. The Chinese agency told the FAA its own tests

found that the insulation burst into flames, but the FAA brushed this

off, because the tests conducted by the Chinese were not required

by the FAA. "While the tests you conducted are illustrative, they do

not invalidate the certification of the material," the FAA wrote.

In addition, Boeing has developed more stringent tests for its own

internal use, leading to the company's recommendation last year

that the metalized Mylar insulation - still in use on the Swissair

MD-11 - be removed from planes manufactured by McDonnell

Douglas, which Boeing acquired in 1997. The FAA technical

center in Atlantic City also issued a report in September 1997

declaring current testing methods inadequate.

Swissair crash was factor

But FAA headquarters did not consider the matter urgent until after

the crash of Swissair Flight 111. Investigators found pieces of

metalized Mylar in the wreckage, although no burned pieces have

been found. The first major portions of the wreckage were dredged

from the ocean floor only recently. Still, investigators are examining

whether these insulation blankets may have played a role in the crash.

Investigators found that metalized Mylar had been implicated in at

least three major aircraft fires, in China, Italy and Denmark.

Although the insulation blankets were not a source of ignition, they

erupted into roaring fires when subjected to electrical short circuits.

No one was killed in those fires.

Thomas McSweeny, the FAA's associate administrator for

regulation and certification, said further tests at the FAA's technical

center in Atlantic City proved that most other insulation used in

airliners also would almost certainly fail any new flammability tests.

The materials also did not do well in the tests developed by Boeing

and used by the Chinese, he said. This includes the foam used in

Airbus products and the metalized Tedlar used on Boeing planes, he said.

The `Q-Tip test'

Boeing's Tedlar insulation technically passed the company's test -

called a "Q-Tip test" because it involves dropping a burning swab

onto insulation samples - but full burn tests conducted at the FCC

center in Atlantic City showed Tedlar also would feed a fire under

the right circumstances. Airbus' insulation foam "does not perform

very well" in the swab test, he said.

McSweeny said the only clearly acceptable insulation at this point is

either Fiberglas or a material known as Curlon. Those two

products then are wrapped in a polyimide film, commonly known

by its DuPont trade name, Kapton.

McSweeny said the FAA will consider any airliner using those

types of insulation to be grandfathered in, if any new regulations are adopted.

Lockheed, by coincidence, used acceptable insulation when it built the tri-engine

L-1011 jet.  Ron Hinderberger, Boeing's director of aviation-safety

investigations, said he does not consider the FAA's statement an

overreaction. He noted that Boeing already used more stringent

tests and added that aviation constantly evolves to produce better and safer

products. Hinderberger also said that Boeing agrees with the FAA's decision

not to issue an immediate order. He said Boeing has no record of

any passenger death related to an insulation-fed fire.

A spokesman for Airbus Industrie said the European consortium

could not comment on the FAA's stance, because it does not have

enough details. Likewise, the Air Transport Association, which

represents major airlines, said it could not comment. But an airline

executive who asked not to be named said the industry was

surprised by the action and found McSweeny's comments

confusing. "We find it very strange he's making definitive statements

like that when it's not clear he's tested all this material," the executive said.

What it could cost

The stakes are high for airlines. The FAA said it has not calculated

the cost to the airline industry to replace the insulation. But

manufacturing and airline sources said it would likely be more than

$1 billion and, perhaps, much more. Some experts estimated total

replacement could run as high as $3 million a plane, although

manufacturing sources said that figure may be inflated.

Jim Hall, chairman of the National Transportation Safety Board,

said he could not comment on the technical details of the FAA plan