The federal government unveiled a plan yesterday to tighten air cargo security by checking the backgrounds of workers who handle freight and by restricting access to sections of airports used for loading and unloading cargo.

The long-awaited plan from the Transportation Security Administration also requires cargo airlines to screen people who board their planes. Freight forwarders -- agents who accept packages and arrange shipment -- must make sure cargo does not include bombs, guns or stowaways.

However, the plan contains few details about how the TSA expects the freight industry to accomplish those goals.

"These proposals would fill gaps in existing air cargo security regulations to mitigate the threat of terrorism to this vital industry," said the proposal, which was signed by TSA chief David M. Stone and listed in the Federal Register.

Critics say it is foolish to carefully screen people and luggage but not the cargo that is carried on passenger planes.

Currently, air cargo loaded onto passenger aircraft must be shipped by a company that has registered with the government. Cargo airlines have security plans, and some cargo is randomly inspected.

Late last year, Homeland Security officials said intelligence indicated al Qaeda might hijack cargo planes and attack nuclear plants, bridges or dams.

The plan does specifically call for companies to submit personal information about freight workers so their names can be checked against terrorist watch lists. The checks would include officers, directors or anyone who owns at least 25 percent of a freight forwarding company.