The calls came at a Washington conference that explored how to keep flying safe in an era when most major airlines, including US Airways, the dominant Philadelphia carrier, have collectively outsourced more than half the maintenance of their aircraft to contractors in this country and abroad.

Speaking on a panel, Deborah Hersman, a member of the National Transportation Safety Board, noted that her independent agency could only recommend that the Federal Aviation Administration adopt tougher rules to prevent airline accidents. The FAA often doesn't adopt better procedures or practices until after a serious mishap, she said.

"It does take a death toll before changes are put in place," she said.

The conference built on reports in the last three years by the U.S. Department of Transportation's inspector general and by Consumers Union, publisher of Consumer Reports, that found large gaps between the standards major airlines use when they maintain their own planes and what's required of contractors.

According to the Transportation Department, nine major air carriers, including America West, which merged with US Airways in 2005, increased the percentage of heavy maintenance outsourced to certified repair stations from 34 percent in 2003 to 67 percent in 2006.

The conference was sponsored by the Radnor-based Business Travel Coalition, representing corporate travel managers, and the Teamsters union, whose members include mechanics at major airlines.

There have been no multi-fatality accidents for major U.S. airlines since 2001.

But 21 people were killed in 2003 when an Air Midwest commuter plane, operating as a US Airways Express carrier, crashed near Charlotte, N.C. The safety board found that improper work done on the plane by a contractor was one of the causes, and said Air Midwest and the FAA had failed in their oversight duties.

William McGee, a Consumer Reports contributing editor who wrote the magazine's report, told conference participants in Washington and online that overseas repair facilities were subject to less oversight than the airlines' in-house shops.

Among other problems McGee said he had found in a nine-month investigation was that repairs at foreign shops didn't have to be done by a licensed mechanic as long as someone with a license signed off that the work had been done properly. Also, employees of most overseas shops aren't subject to drug and alcohol screening or security background checks as they are in this country, he said.

"We're truly in uncharted skies with what's happening now," McGee said.

Rep. James J. Oberstar (D., Minn.), chairman of the House Transportation and Infrastructure Committee, said in a videotaped address to the group that legislation the House passed last year to reauthorize the FAA would require the agency to raise the requirements on overseas facilities. The legislation is pending in the Senate.

Sen. Claire McCaskill (D., Mo.), a member of the Commerce and Homeland Security Committees, said in another videotaped address that she found it "kind of weird" that passengers couldn't carry shampoo on an airline flight yet there were lax security standards for overseas repair shops.

Sarah MacLeod, executive director of the Aeronautical Repair Station Association, the only industry representative among the panelists, said most of her members were small businesses. They need help from the major airlines that hire them to develop better training manuals and educate mechanics so they can do a better job, she said. But, she said, "contract maintenance is here to stay."

Kevin P. Mitchell, chairman of the Business Travel Coalition, said he had set up a group he named the Coalition to Legislate Aircraft Maintenance Outsourcing Reform, or CLAMOR, to press Congress to adopt more stringent rules on contractors.

Mitchell said that he had invited FAA and airline officials to participate in the conference, but that they had declined.