Officials at Dulles International and Baltimore-Washington International airports said they are considering the replacement of federal airport screeners at security checkpoints with workers employed by private contractors.

The Transportation Security Administration this week invited airports to apply to leave the federal security screener system and return to private screeners. The government took over airport screening after the Sept. 11, 2001, terrorist attacks and is planning a transition for approved airports by spring or summer 2005.

Several airports have said private contractors might provide more staffing flexibility and might be more responsive than the federal government to hiring more employees when needed. This summer, passengers at Dulles waited more than an hour at times to pass through security as air traffic surged there with the launch of Independence Air.

"The issue of the long lines -- that's probably where we're most concerned about customer service issues," said Tara Hamilton, spokeswoman for the Metropolitan Washington Airports Authority. She said the concerns mostly pertained to Dulles and not Reagan National Airport, which the authority also operates. "We've not made a decision at this point."

A spokesman for BWI said the airport needs more information about a shift to private screeners. Like many major airports, BWI said it wants to learn more about liability in the event of another terrorist attack.

"Some pretty significant questions need to be answered," BWI spokesman Jonathan Dean said.

The TSA suggested in its announcement this week that airports would be protected by federal laws that limit tort liability in case of terrorist attack, but it did not specify the exact terms. Airport officials are concerned about what would be covered, said James McNeil, chief executive of McNeil Technologies Inc., a security firm that employs screeners at the Rochester, N.Y., airport. "If they can get some indemnification, that will play a huge role" in decision making, he said.

The TSA has set up a complicated process for the transition. Airports apply to the TSA for approval to "opt out" of the federal screening program. U.S.-based private security firms also apply to the TSA to be approved as security contractors. The TSA would then select the security firm for each airport, and the company would sign a contract with the agency, not the airport. The firms must abide by the same security standards as the TSA's, and federal supervisors already stationed at airports would oversee the contractors.

Airports said the private security option is attractive because they can be more creative with screeners' schedules and duties. Some airports would like to have screeners working for private companies staff security checkpoints during busy travel times and give the employees other airport duties, such as cleaning or wheelchair services, during slower periods. Some airports have discussed keeping TSA screeners at one terminal and stationing privately employed security screeners at other security gates.

Several months ago, lawmakers and lobbyists estimated that one in four of the nation's airports expressed interest in switching to private security firms, but now security contracting companies said they do not expect more than two dozen airports to apply. Many of the applicants, they said, will likely be mid-size or smaller airports.

"We feel, eventually, most airports will opt out" of the federal program, said Gerald L. Berry, president of Covenant Aviation Security LLC, which employs screeners at San Francisco International Airport through a TSA pilot program. "But they're not in a hurry."

TSA said security companies must provide comparable pay and benefits to their workers and must give priority in hiring to current TSA screeners. But that isn't reassuring to many TSA screeners, said Ron Moore, a screener at BWI and president of Local 1, the American Federation of Government Employees union.

"We feel protected as federal screeners because we don't feel we can be pressured by airlines or airports," Moore said. "The passengers seem to respond better to us because we're federal. It would be a shame to start to break that."

Pemela Lawrimore checks passenger Joy Sandler at Dulles International Airport in 2002, after federal screeners replaced private security workers at airports.