Despite nearly three decades of warnings from safety experts, the U.S. still has more than 300 runways at commercial airports that don't have adequate overrun areas to help avoid accidents like the crash two weeks ago of an Air France jumbo jet that ran off a Toronto runway into a ravine.

Federal standards require an extra 1,000 feet of overrun area at both ends -- where planes can skid to a stop without hitting obstacles -- but under current rules, airports aren't required to retrofit existing runways. The National Transportation Safety Board has been pushing for runway-overrun improvements since 1977, and issued recommendations again in 2003 after a Southwest Airlines jet went off the runway in Burbank, Calif., and slid into a gas station.

The Federal Aviation Administration last year began pushing airports to install a patch of a new material that can quickly stop jets if they roll or skid off the end of a runway. The FAA considers the material -- which is a mixture of water, foam and cement called Engineered Material Arresting System, or EMAS -- as an acceptable alternative to a full 1,000 feet of runway overrun. Just 400 feet of EMAS can stop a passenger jet traveling 70 miles an hour without causing substantial damage to the airplane.

The material has already saved airplanes and their passengers. At Kennedy, a waterfront airport in New York where a test bed was installed seven years ago on Runway 4R, three planes have already been saved from a plunge into the water by EMAS -- one an American Eagle turboprop, and the other two wide-body cargo jets. Runways at other waterfront airports, including La Guardia in New York and Logan in Boston, have also been fitted with EMAS.

In addition, the runway in Burbank where the 2003 crash occurred has been fitted with the EMAS, as has the runway in Little Rock, Ark., where an American Airlines MD-80 careered off the end in 1999 after trying to land in a thunderstorm and crashed into the Arkansas River, killing 11 people.

The FAA says construction of runway safety areas will be completed at 38 airports around the country in the current fiscal year ending in October, including Boston, Columbus, Ohio, Fort Lauderdale, Fla., Houston, Jackson, Miss., Lansing, Mich., Long Beach, Calif., San Antonio, Texas, and Tampa, Fla.

"We're trying to accelerate airports that don't have it," said FAA spokeswoman Diane Spitaliere. Federal funds help pay for the work: EMAS, which is manufactured by a unit of Group Zodiac SA, can cost $2 million to $4 million per runway, the FAA says.

Ms. Spitaliere of the FAA says adding safety areas at some runways is still extremely difficult because of a lack of real estate or because of environmental concerns. "It's not realistic that we just go out and tell airports to do it," she said. The FAA says it doesn't have a list available for the public on which runways have adequate runway safety areas, and which don't.

The FAA says there are now 18 EMAS installations at 14 airports in the U.S., and contracts have been signed for four more. In all, a 2000 survey of 1,024 commercial airports in the U.S. showed 45 percent failed to meet safety standards. Ms. Spitaliere says that number has declined as improvements have been built, and now only 38 percent of the 500 largest airports lack adequate runway safety areas.

The NTSB, which in the past has declared the FAA's response to its recommendations for overrun areas "unacceptable," says it now considers the current FAA push "acceptable," spokesman Paul Schlamm said.

Canadian officials are also promising improvements after the Aug. 2 crash of an Airbus A340 in Toronto, which ran off the end of the runway and into a ravine, where it burst into flames. (All 309 people on board safely evacuated.) In 1978, An Air Canada DC-9 crashed into the same ravine, killing two. International pilots' groups pushed for bringing the runway up to international safety standards, which call for a defined "runway safety area" free of obstacles well past the end of a runway. But despite spending billions of dollars on new terminals, Toronto didn't build an overrun area for the Runway 24R.

The Air France crash "is the latest in a series of airline accidents that highlights the dangers of inadequate runway safety areas," the Air Line Pilots Association said in a statement.

Canada's transport minister, Jean Lapierre, has promised swift action on any safety recommendations from the Air France crash, including "whether you need more space at the end of the runway." The Air France plane touched down roughly halfway down the length of the 9,000-foot runway during a thunderstorm.

The Greater Toronto Airport Authority says it doesn't currently have any plans to construct an overrun area over the Etobicoke Creek ravine. Connie Turner, a spokeswoman for GTAA, pointed out that an overrun area wasn't recommended in the accident report on the 1978 Air Canada crash, and Canada's aviation regulations don't require runway safety areas.

Still, the International Civil Aviation Authority has long recommended runway safety areas, and pilot groups have been trying to pressure Toronto to build one. "An arrester bed should have been fitted on this runway," said the International Federation of Air Line Pilots Associations in a statement. "This has been a point of contention between the airport and (the association) for more than 25 years."