The government told cargo and passenger airlines on Monday that they must randomly inspect a certain amount of freight before it is loaded on planes as part of an effort to close security gaps.
Brian Turmail, a spokesman for the Transportation Security Administration (search), said the agency won't disclose publicly what percentage of cargo must be inspected because of security concerns.
Checks of air freight have been spotty, with some airlines conducting limited inspections and others doing little or nothing. Critics contend that leaves open the possibility terrorists could use packages to sneak explosives or even hijackers aboard planes.
Turmail said the airlines will do the inspections under government supervision. The policy takes effect after Christmas.
TSA chief James Loy said in a written summary prepared for Congress that it's difficult to inspect all cargo because "limitations of technology and infrastructure make such an undertaking impractical."
Leon Lalaygian, a pilot who sits on the security committee of the Coalition of Airline Pilots Associations (search), called the requirement a "good initial move."
UPS spokesman David Bolger said the company will review the government's instructions once it has received them.
The TSA also is requiring 15 foreign cargo airlines to file security plans with the federal government, describing their efforts to control access to freight and aircraft. U.S. airlines and non-U.S. passenger carriers already file such plans, Turmail said.
Earlier this month, the Homeland Security Department (search) warned Al Qaeda might be plotting to fly cargo planes from another country into such U.S. targets as nuclear plants, bridges or dams.
Some members of Congress have pressed for more stringent cargo protection, especially for freight carried aboard passenger planes. They say it is foolish to screen passengers and luggage in the cabin but not cargo in the hold.
Rep. Edward Markey, D-Mass., said Monday that random inspections of unknown cargo on passenger planes "provides only slightly more security to passengers than the security system in place before Sept. 11, 2001."
Sen. Kay Bailey Hutchison, R-Texas, welcomed the TSA's announcement but said more work needs to be done. "We need a comprehensive system to better protect Americans from this potential Trojan horse," she said.
Criticism intensified in September when a New York shipping clerk packed himself in a crate and flew undetected to Dallas.