DALLAS -- Dozens of federal inspector credentials giving access to airports have gone missing, an NBC 5 investigation revealed.

According to the investigation, 122 Federal Aviation Administration safety inspector badges have been stolen or lost in the past five years. The credentials are one of the few forms of identification that give complete and unfettered access to airport facilities, including the cockpits of planes in flight.

"The FAA badge is probably of all the badges just as dangerous if not more so than any other," aviation expert Denny Kelly said.

Kelly, a former commercial pilot and a private investigator, said the badge can give a person free access to nearly every secure area of an airport.

"The FAA badge allows you not only on one airline, plus getting through security, it allows you to get on any airline, any airplane, anyplace," he said.

The FAA said it is concerned but insisted the public is not in danger. The agency is taking an aggressive stance to prevent the loss of those badges in the future, the FAA said.

The agency refused NBC 5's request for an on-camera interview. Over the phone, a spokesman could not guarantee that FAA badge holders always go through security checkpoints.

"A guy walks up with that badge and says, you know, 'I'm an FAA guy, here's my badge,' there's nothing they do about it. 'OK, fine, go through,'" Kelly said.

One traveler said the idea of more than 100 FAA badges floating around made her uneasy.

"To think that anybody has access to a cockpit on a plane is particularly scary," Alison Bock said.

The FAA has stopped sending badges through the mail and forbids inspectors from leaving them in their vehicles, where most were stolen.