Hidden away in an office building, dozens of federal air marshals hone the techniques and skills they take onto planes flying in and out of Charlotte every day.

Eyewitness News got a behind-the-scenes look at their training, and asked them to wear helmets to cover their faces because the marshals hide themselves among the businessmen and vacationers and other travelers who flock by the thousands to Charlotte-Douglas International Airport.

“We're there to protect against criminals or terrorist threats against the aircraft, passengers and crew,” said Ray Dineen, special agent in charge.

To get ready, the air marshals' Charlotte office has built everything to make training as realistic as possible, from going through security to simulating check-in to walking into a full-scale mock-up of a jetliner. Once they're inside, they train over and over, hoping to avoid trouble before it happens. But if it's necessary, learning how to win a fight on an airplane.

The seating, aisles, bathroom and cockpit give air marshals a life-sized simulator. For security reasons, Eyewitness News can’t describe the elaborate hostage and gunfire scenarios they train on, but the camera crew could tape how air marshals train to deal with suspicious or troublesome passengers.

“Sir, down on the ground down on the ground, you're under arrest. Stop fighting me, sir,” a federal air marshal shouts.

Every air marshal learns close-quarters fighting because there's little room to maneuver on a plane, and all of them also learn how to blend in, looking and acting just like the real passengers on board every flight they take, until they're needed.

“We've had situations when you have distressed people behaving irrationally, which need to be addressed. We've had assault on flight crews,” Dineen said.

Just after Christmas air marshals in Charlotte arrested Melanie Sundeen. She's now charged in federal court with threatening a flight attendant and a passenger and with assaulting the air marshals who cuffed her and took her off the plane.

Until the arrest, other passengers had no idea the air marshals were there.

“They would not know that we're there or where we are, and that's how it should be so we can react appropriately to any incident or threat on an airplane,” Dineen said.

“So, if people are on an airplane and they're looking around trying to figure out which one is the federal air marshal?” asked reporter Jim Bradley.

“They're wasting their time,” Dineen said.

For security reasons Charlotte's federal air marshal office won't say how many agents it has or how many flights a day air marshals are on.

LINK:Federal Air Marshal Service