As the U.S. Transportation Security Administration struggles against harsh criticism of its new see-through-clothing scanners and enhanced pat-downs of airline passengers at security checkpoints, some airports are considering joining the 17 airports around the country that have replaced federal inspectors with employees of private security firms.

The move is being pushed by Rep. John Mica (R., Fla.), who helped write the law creating the TSA in 2001. Though private firms are required to adhere to TSA screening standards - including the new scanners and pat-down procedures - Mica and other advocates say competition will keep the TSA more accountable, possibly save money, and provide friendlier customer service.

Kansas City International Airport director Mark VanLoh noted that his airport had won the J.D. Power award for customer satisfaction among medium-size airports the last two years, and he gave its private security firm a big share of the credit.

"We think it has a lot to do with screeners," he said. "If you go to work for the federal government, once you're in, you're going to retire here. But this company, they have a five-year agreement; if they don't like you, and you don't perform to their standards, you're on the street.

"So you know you have to be at the top of your game. And it shows."

The TSA maintains that is the kind of service the agency expects at every airport, with either public or private security.

"TSA is committed to providing both world-class security and world-class customer service," said spokeswoman Sari Koshetz. "And over the past two years, 100 percent of our officers have received additional training focused on engaging with passengers in a positive and professional manner."

Despite the advocacy of Mica and others, there is little data available comparing the performance of private contractors with that of the TSA. The TSA would not release copies of either its contracts with private firms or internal studies of their performance, saying they contain "security-sensitive information" that must be reviewed and redacted.

The revival of private security firms worries safety advocates such as Paul Hudson, executive director of the Aviation Consumer Action Project and a former member of the TSA's Aviation Security Advisory Committee.

Hudson, whose daughter was among 270 people killed in the 1988 bombing of Pan Am Flight 103 over Lockerbie, Scotland, said private security has a worrisome history of fatal inconsistency. The TSA was created after private contractors allowed terrorists to board planes on Sept. 11, 2001.

"The past experience before 9/11 is that sort of system quickly deteriorates. They go for the low bidder," said Hudson, whose Sarasota, Fla.-based group was founded by consumer advocate Ralph Nader. "The federalization of security is very important. Whether you have a private system or not, it needs to be carefully monitored and it needs to have standards that should be higher."

The TSA and advocates of private companies insist those goals are met. Because TSA contracts with and oversees private contractors at airports that use them, the agency says there is no security difference between TSA and private screeners.

"TSA's security protocols and standards are the same for all commercial airports nationwide," Koshetz said. "At airports participating [in the private-security program] a TSA federal security director and management team are still responsible for overseeing the security operations. Contract screeners must meet the same requirements as federal screeners in the areas of hiring, training, and performance."

San Francisco and Kansas City airport officials using the private security said they did not review details of the program because the federal agency managed it for them. "The airport doesn't get involved at all," said Michael C. McCarron, spokesman for San Francisco's airport.

Other airports with private screening contractors include smaller sites such as Key West, Fla.; Rochester, N.Y.; Sioux Falls, S.D.; Tupelo, Miss.; and Gallup, N.M.

San Francisco's contract is with Covenant Aviation Security of Florida, while Kansas City's is with Cleveland-based First Line Transportation Security. Neither company responded to requests to discuss deals or operations.

Big money is involved. While 2010 contract details are not available, the TSA reported that Covenant's previous four-year deal with San Francisco, signed in 2006, was worth $314 million, while FirstLine's 2006 contract at Kansas City was worth $173 million. The TSA has certified more than 30 companies to compete for the service.