(AP) While passengers and pilots pass through tightened airport security checkpoints, baggage handlers and other workers still bypass screeners and metal detectors by using identification cards that open locked doors.

The government is considering how to fix this flaw in the security net that regulators have been strengthening since Sept. 11. Critics say they are moving too slowly.

“There's a hole in the system that's bigger than a barn door and should send shudders up the spine of the traveling public and those responsible for the security of our nation's air transportation system,” said commercial airline pilot Robert Held, who has flown for 14 years.

John Magaw, who heads the new Transportation Security Administration, or TSA, said his agency is looking at ways to restrict access to secured areas to “improve security and ensure the integrity of our nation's airports.” Secured areas are those places beyond airport passenger checkpoints where employees can walk up to airplanes.

Among proposals under study are improved background checks, tamperproof identification cards and rules that send all airport employees through screening checkpoints, TSA spokesman Jonathan Thompson said.

Pilot programs to test various security procedures are planned for 20 airports, the agency said. Under the new airline security law, TSA must inform Congress this month of its progress, with reports expected Monday.

Mary Schiavo, a former Transportation Department inspector general, said TSA has been so concerned with stopping terror hijackings that it hasn't moved quickly to prevent bombs from getting onto planes through the cargo hold or on a food cart.

“We haven't had an attack launched through that access,” said Schiavo, now a lawyer representing victims of airplane accidents. “I don't think they're very worried about it.”

Aviation experts fear terrorists could use employee entrances to bypass security checkpoints and plant bombs or weapons aboard parked airplanes.

“It is a weakness in the system that's exploitable by a terrorist group or someone who wants to make use of it,” said former Federal Aviation Administration security director Billie Vincent, president of Aerospace Services International in Chantilly, Va.

Reports from both the Transportation Department's inspector general, Kenneth Mead, and the FAA said airports have failed to restrict access to runways and airplanes adequately.

While rules vary by airport, those who can obtain access cards include cleaning crews, maintenance workers, baggage handlers, construction workers and employees who stock airplanes with food and drinks.

The inspector general said his investigators successfully entered unsecured ramps, runways, cargo areas and other places beyond security checkpoints more than two-thirds of the time during a recent visit to eight major airports. FAA special agent Bogden Dzakovic said his undercover team entered a secured area of a major airport 85 percent of the times they tried.

Some of the special identification cards were in the hands of more than 400 airport employees recently arrested on fraud and immigration charges as part of a Justice Department sweep.

“We need better systems that provide protection for our secured areas,” said House Transportation aviation subcommittee Chairman John Mica, R-Fla. “There's no question we're vulnerable.”

The problem has long been known. In July 2001, the FAA adopted rules that allowed the agency to levy fines of up to $11,000 against airport employees who hold security doors open for colleagues, lend a badge to a co-worker who forgot it at home or allow friends to visit restricted areas.

Airport officials acknowledge the problem.

“The bottom line on access control is can it be improved? Can it be enhanced? Certainly,” said J. Spencer Dickerson, executive vice president of the American Association of Airport Executives. “You're always finding ways to continually improve the system.”

Separately, a Minnesota company is taking heat from the Minnesota Civil Liberties Union over facial-recognition software the company says can be used at airports to fight terrorism.

The criticism followed a report by the American Civil Liberties Union earlier this week, which said a system powered by software from Minnetonka-based Visionics Corp. failed 53 percent of the time during testing at Palm Beach (Fla.) International Airport.

“The technology doesn't work,” said Charles Samuelson, executive director of the ACLU's Minnesota branch. “It's not as good as they claim it is, and it never was.”

Samuelson said the organization also opposes the system because it intrudes on privacy rights.

But a Visionics spokesman defended the product and faulted improper lighting and camera angles for the bad results. In tests at Boston's Logan International Airport and Dallas-Fort Worth International Airport, there was successful recognition more than 90 percent of the time, Meir Kahtan said.

“If 80 percent of the (Sept. 11) hijackers had been caught, wouldn't that be better than none?” Meir said.

Further backing up Visionics on Friday, Raytheon Co., which makes the system that uses Visionics software, said it “achieved a high rate of successful matches in field tests recently carried out” at Logan.

As a result, “Raytheon will be able to recommend approaches to using biometric tools to provide higher levels of security at U.S. and international airports,” said Ramsey Billups, Raytheon technical director of Biometrics and Secure ID Systems.

But the ACLU still thinks the Palm Beach tests are enough to continue its campaign against the system.

In Palm Beach, the ACLU said, results of the first four weeks of an eight-week study found that the system made a match only 455 out of 958 times that volunteers went through it.