(AP)  Four dozen commercial airline pilots selected for a test program are expected to fly passenger planes while wearing a gun beginning this spring.

But the 48 will have to carry their .40-caliber semiautomatic pistols in locked cases inside nondescript bags while walking through the airport. The guns have to be put back in the case if a pilot leaves the cockpit in flight.

The Transportation Security Administration announced on Tuesday that its final plan for arming pilots would limit to the cockpit their authority to carry a gun in a holster.

Pilots don't want to carry a weapon in a locked case, saying it's more likely to fall into the wrong hands if it has to be transferred back and forth.

"We propose that we carry the weapon concealed personally on our body because that is the safest, most secure way for us to transfer the weapon," said Al Aitken, spokesman for the Allied Pilots Association.

TSA spokesman Robert Johnson said the law says pilots can carry guns for only one purpose: to defend the cockpit during flight.

"We don't want that weapon floating around inside the cabin," Johnson said.

The TSA plan mirrors the recent recommendations by a task force comprised of agency employees who met with pilots, airlines and aircraft manufacturers.

Pilots will be required to undergo psychological and background checks before being selected for a five-day training program that will include lessons on marksmanship, defensive tactics and legal policies, Johnson said. After finishing training, pilots would be issued .40-caliber, semiautomatic pistols.

Some pilots object to the psychological testing they'd have to undergo if they volunteered for the program. Others say it will make the program better by weeding out people who might have a hard time killing someone.

Congress, which overwhelmingly approved arming pilots, didn't give the TSA any money to train pilots or pay for guns. The agency cobbled together $500,000 from various accounts for a test program that can only accommodate the 48 pilots.

Johnson said the agency asked pilots' groups for nominations and expects to have them in the next week or two. The TSA will select the class, and those who complete the training will be sworn in as federal flight deck officers.

The agency has asked for $20 million to run a broader program.

Only pilots who volunteer will carry weapons. It's unclear how many of the nation's 100,000 commercial passenger pilots will choose to participate, with estimates varying from a handful to 30,000.