SEATAC, Wash. -- They're armed, under cover and trained to take down terrorists.

Hear from federal agents who just might be in the airplane seat next to you as the holiday travel season kicks off next week.

The federal agents we spoke to are not air marshals, but they are armed every time they set foot into an airport or on an airplane.

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They'll be flying this holiday season just like many of you. But unlike you and me, the agents have access to the information and security secrets that dictate what we all have to go through in order to get to our destinations safely.

"On and off duty, we're armed, because it's a 24-7 job," said one agent.

"After Sept. 11, they realized how many air marshals they could have just by federal agents flying armed," said another agent.

They look like any other passenger you might see at the airport. And that's the point -- to blend in.

"We carry our weapons with us so that when we get to where we are going, we can immediately go to work."

For the last several years, federal agents from a number of law enforcement agencies have been patrolling commercial airplanes whether they're flying for work or not.

"You know, I have looked for them, and I've never seen them. I can't tell. They're invisible," said Craig Sowash, of Portland.

They are invisible and trained to be vigilant.

Without divulging any security secrets, the officers tell us what they look for.

"You look for anything out of the ordinary," said an agent. "Anybody that's nervous, anybody acting different, acting strange and just paying attention to them."

"And it doesn't even have to be terrorists, it can be just somebody who's just not right. They didn't take their medication or they are mentally disturbed and they are going tohave a problem on that aircraft."

As far as the liquid ban enacted this summer, the agents say the restrictions are part of what have made flying safer since Sept. 11, 2001.

"The less they allow on the planes makes it easier," an agent said.

"We are flying in a new era, so people just need to be more patient and realize a little inconvenience is well worth it."

"I (think it's a) little silly, a little extreme, I think. Chapstick? I mean, come on," said Liz Gould of Los Angeles.

"If people are hindered by them or they don't like them, then I think they should find another way to travel," an agent said.

And travelers should prepare for more regulations.

The armed officers say it's only a matter of time before terrorists come up with another deadly tactic.

"It's going to change in the future-- more restrictive-- the public is going to have to realize bad guys adapt so we are going to have to adapt to stop them," an agent said.

Next week, more than 100,000 Thanksgiving travelers will pass through Sea-Tac International Airport each day.

Hopefully, packed away with their plastic bags of 3-ounce liquids is some patience.

"There are things that go on behind the scenes that the public just doesn't know about and if it seems out of the ordinary and they are inconvenienced by it they just need to grin, take a deep breath and say it's for my own good," one of the agents said.

Passengers far out number the armed agents who fly everyday. That's why the officers we spoke to say the best line of defense is you.

As you fly over the next few weeks, stay alert and report anyone or anything that seem suspicious.