"Are the costs going to outweigh the benefits?" asked Cris Jensen, director of the Elko Regional Airport. "We're not sure."

Advocates of private screeners had predicted that dozens of airports would jump at the chance to make the switch, saying the bureaucracy inherent in a government agency - the Transportation Security Administration - slowed staffing decisions at the country's 450 commercial airports. Security lines snaked through some terminals while screeners elsewhere at an airport sat idle.

Elaine Sanchez, spokeswoman for Las Vegas McCarran International Airport, explained why most airports are sticking with the federal screeners: "In a word, liability," she said. Sanchez and other airport officials said they are concerned about potential lawsuits: People might sue an airport where private screeners failed to prevent terrorists from launching an attack.

After the attacks of Sept. 11, 2001, the government created a fund that paid victims and their families if they agreed not to sue airlines, airports, security companies and others. The participation rate was 97 percent; only about 80 suits rose from the terrorist strikes.