WASHINGTON — U.S. pilots and flight attendants are working harder as passenger loads increase after airline bankruptcies, causing fatigue that endangers safety, labor unions told Congress yesterday.

Pilots routinely work as long as 15 hours a day, with flight time limited to eight hours, said Terry McVenes, safety chairman for the 60,000-member Air Line Pilots Association. "The bankruptcy era following 9/11 has cut deeply into the safety fabric," he told a House subcommittee in Washington.

Pat Friend, president of the 55,000-member Association of Flight Attendants, said attendants weary from too little time between flights sometimes nod off in their seats or forget tasks such as setting evacuation slides to deploy automatically.

The testimony from six aviation unions may boost pressure on Congress to tighten safety laws, forcing airlines to hire more people. Democrats sympathetic to labor groups won House and Senate majorities in November.

McVenes said in an interview after the aviation subcommittee hearing that he wants regulators to cut the maximum 16-hour duty day for pilots to 12 or 14 hours, or whatever level is determined best after scientific study.

U.S. airlines cut workers after the Sept. 11 terrorist attacks and during four years of losses that followed. Four major U.S. airlines filed for bankruptcy: UAL Corp.'s United Airlines, Delta Air Lines Inc., Northwest Airlines Corp. and US Airways Group Inc.

Airline employment in 2005 fell to 553,000, the lowest level in a decade, the Air Transport Association airline trade group said in its 2006 annual report. The peak was 680,000 workers in 2000, the group said.

"All aspects of the aviation industry are doing more with less," said David Castelveter, spokesman for the Washington-based trade group. "The harsh reality is that for carriers to survive, they had to make hard choices."

The industry's smaller workforce is handling more travelers. Traffic, or miles flown by paying passengers, rose 2 percent to a record last year, according to the trade group.

Job cuts didn't reduce safety, Castelveter said. "It is something that will never be done," he said.

U.S. airlines in 2006 continued to have the lowest accident rate in all of civil aviation, the National Transportation Safety Board said in a March 13 report. The fatal accident rate is .018 per 100,000 departures, the board said.

"The system is safer than ever," the Federal Aviation Administration's top official, Marion Blakey, told a House Appropriations Committee panel at a separate hearing yesterday.

But delays will worsen if the FAA doesn't hire more air-traffic managers, Steve Baker, president of the FAA Managers Association, told the House aviation panel. His group is pressing for a 14 percent increase in managers. Delays rose last year to their highest level since 2000.