Security at air cargo terminals is being strengthened out of concern that these facilities are getting too little attention in the push to better protect passenger planes.

The Transportation Security Administration is developing security programs for cargo carriers, just as it is for commercial passenger airlines, said Bill Wilkening, manager of dangerous goods and cargo security. "We have a whole dedicated program just for cargo and dangerous goods," he said. "We do focus on cargo as much as we focus on baggage and passengers. A lot of it is behind the scenes."

Cargo isn't screened like passengers and luggage are and air marshals must focus on passenger cabins, security experts and pilots said.

"If you improve security to the point that you make the passenger side impregnable, any person looking around the airport is going to say, 'What's my easiest point of entry?'" said Kevin Scheiterlein, a FedEx pilot for 13 years. "All they have to do is look across the airport to the cargo side."

The issue is of such concern that Air Line Pilots Association President Duane Woerth raised it during a meeting earlier this spring with John Magaw, undersecretary of transportation for security. The union and the security agency have been working on the issue ever since.

"Cargo operations are currently at significant risk due to the absence of basic security measures applied to protection of the aircraft, cargo and the flight crew," Woerth wrote Magaw. "Because of these deficiencies, we believe it is entirely possible that terrorists may opt to commandeer a cargo aircraft, instead of a passenger aircraft, and use it as a guided weapon against persons and property on the ground."

Among the problems cited by pilots and security experts: Cargo areas are often located far from the passenger terminals, where security may not be as tight. Trucks can drive right up to the planes to load cargo and many flights take off at night.

"Cargo aircraft are usually large, contain a great deal of fuel and there are relatively few security precautions taken around the aircraft," said Rep. John Mica, R-Fla., chairman of the House aviation subcommittee.

Industry officials say they have had security procedures in place even before Sept. 11, including screening all visitors and crew members with metal detectors, and have tightened them since then.

"For us, safety has always been a key concern and we're going to do everything we can to make sure every aircraft we put in the air is safe for our employees, the general public and the nation," said Mark Giuffre, a spokesman for United Parcel Service Airlines. "We've always had strong security procedures."

The TSA also has worked to keep bombs out of cargo carried on passenger jets.

"Everything is a high priority," agency spokeswoman Mari K. Eder said. "What you see is more public attention on the mandates set by Congress. That does not mean anything else is shunted to the side."

Government and industry officials say they have improved cargo security since Sept. 11, and are working to make it even tighter. Airlines and freight forwarders, who assemble packages from many different companies, can no longer accept packages from shippers they don't know, for instance.

Air cargo is a significant business for passenger airlines, bringing in $13 billion last year, and accounts for about 12 percent to 15 percent of their revenue, according to the Air Transport Association, the trade group for the major airlines.

But the cargo isn't screened for explosives or weapons, the people handling the package may not be known to the airline and safeguards can be circumvented, experts said.