TSA said scanning devices that would have allowed passengers to keep shoes on were inadequate.
WASHINGTON - After spending millions of dollars testing four different scanning devices that would allow airline passengers to keep their shoes on at security checkpoints, the U.S. government has decided for now that travelers must continue to remove their footwear, by far the leading source of frustration and delays at the airport.
The Transportation Security Administration said it rejected all four devices because they failed to adequately detect explosives and metal weapons during tests at various airports. One of the scanners is now used in airports in 18 countries.
Last September, Secretary Janet Napolitano of the Homeland Security Department raised hopes when she said that research and development on scanning machines was progressing and that air travelers would eventually be able to keep their shoes on.
But nearly a year later, the TSA, which is overseen by Homeland Security, said it was not any closer to a solution. Lisa Farbstein, an agency spokeswoman, would not address why it rejected the devices.
"But overall, the machines we tested didn't detect all the materials we were looking for," she said.
Shoes were ordered off after Richard Reid tried unsuccessfully to detonate explosives in his shoes on a flight from Paris to Miami in 2001. Since then, the government says it has found a host of dangerous items in passengers' footwear and says it will not reconsider the requirement until it is satisfied with a scanning technology.
In 2007, TSA tested a General Electric shoe scanner at Orlando International Airport. The next year, it tested two scanning machines made by L-3 Communications at Los Angeles International Airport. But none passed agency muster.
It also tested a device called MagShoe, which is intended to detect metal and is made by IDO Security, an Israeli firm that deploys the scanner in hundreds of airports and cruise ships around the world.
IDO President Michael Goldberg said the scanner can detect metal explosives, but not plastic explosives.
Goldberg said the machine performed flawlessly in tests with the TSA. But the agency did not think so.
He said no current technology can detect all of the various chemical compounds used as explosives. Current X-ray machines used to scan shoes can detect metal but are not much help in finding liquids or gels that can be used as explosives.
The government has a $1.4 million contract with Morpho Detection, a subsidiary of the French defense giant Safran, to develop a shoe scanner.
Morpho's machine can detect chemical compounds and metal objects, said Brad Buswell, the president of Morpho and a former Homeland Security official.
"Our device can detect items to see if there is an explosive in a shoe or simply a pair of Dr. Scholl's inserts," Buswell said.
He said the company will be testing a prototype with the TSA this year.
Many security experts say the security agency is too focused on technologies for intercepting things -- guns, knives, explosives -- instead of focusing on stopping people.
Rafi Ron, the former chief of security for Israel's Ben Gurion Airport, said TSA should abandon its shoe-removal policy.
"They need a more passenger-based approach instead of looking for items," Ron said.
The Israeli model is based on interviews and profiles of passengers. Screeners quickly try to decide whether a passenger poses a threat based on reactions to a set of questions.
Critics said the Israeli approach would be unworkable in the U.S. and cause longer lines. Some 803 million passengers passed through airports last year in the U.S. Israel, by contrast, screened about 12 million passengers. Critics also say such techniques can turn into racial profiling and other forms of discrimination.
The TSA said that its security measures focus on the risks that passengers pose and that the vast majority of travelers in the United States would continue to take off their shoes.