Record numbers of people are now taking to the skies, filling planes and counting on thousands of Federal Air Marshals to protect them.
"Our job is to be on that aircraft and to stay focused and prepared for the threat, because you never if there's going to be a threat," said Thomas Kelly, the Assistant Supervisory Air Marshal in Charge at the TSA's Public Affairs Office.
Long before they ever set foot on an airplane, Federal Air Marshals begin their intensive training not far from Texas, only a short one-hour flight from Dallas-Fort Worth, at the Federal Law Enforcement Training Center in Artesia, New Mexico.
"A lot of people here, I think, that is their natural instinct, is to serve and protect people in any way you can, try to keep as many people as you can safe," said one new air marshal, whose name was withheld to protect her identity.
They may be the most secretive of all federal law enforcement agencies, and the faces of all but a few air marshals are kept hidden to protect their identities.
"We work hard to maintain our anonymity while we are on board the aircraft," Kelly said. "That's why we are plain-clothed and we blend in with the passengers, and we want the terrorists to not know where we are at any given time."
The government says there are thousands of Federal Air Marshals, but won't give an exact number.
Sixteen years after the attacks of Sept. 11, 2001, the Transportation Security Administration has been hiring more air marshals after a long lapse.
Those hired over the past two years are the first to join the service since 2011.
More than two-thirds of air marshals have prior law enforcement experience, but regardless of their background, all of them begin their new careers at the rarely seen Federal Law Enforcement Training Center in Artesia.
"We receive a variety of students with various backgrounds, some with prior law enforcement and military experience, others that have never touched a firearm in their lives," said Matt Lear, supervisor of Federal Air Marshal Training in Artesia.
"We have to start at the lowest point, we acclimate them to the firearm, we teach them how to handle the weapon," Lear said.
Flying at 30,000 feet, and traveling at 500 miles an hour, Federal Air Marshals must be deadly accurate.
"You need to be an expert shooter, you need to be able to handle yourself physically, be in shape, and you need to be mentally prepared," Lear said.
New air marshals training in Artesia must perform better on the gun range than any other federal service there.
"If their accuracy isn't to the tightest pinpoint, then they run the risk of injuring other individuals, innocent individuals, aboard that aircraft," Lear said.
More specialized training follows in Atlantic City, New Jersey, where the new air marshals will learn how to stop a terrorist threat in mid-air.
"Federal Air Marshals are trained to respond to the threat no matter where it is on board the aircraft," Kelly said. "We want to keep our adversary on their toes. You never know where we're going to be or when we're going to pop up."
Many new air marshals are women, increasing the level of deterrence on board planes.
"By adding more females, by adding more diversity in general, the type of person you expect to be Federal Air Marshal may not be one, so you might be putting your eye on the wrong person," the anonymous student said.
The average yearly salary is $44,000, and the job isn't easy.
The typical Federal Air Marshal flies more than 180 days each year, covering hundreds of high-risk flights.
"You want to look like an actual passenger, so you have to play the part, but you are at all times, spanning or scanning the aircraft or the cabin for anything out of the ordinary," Lear said.
The youngest air marshals now training in Artesia were just five years old on 9/11.
"Growing up in the whole 9/11 culture is knowing that you have to be there for your neighbor and be there for everybody else. You want to see something, say something, but if you can for example join the team, then you should," the student said.
There aren't nearly enough air marshals to be on every flight, and several reports suggest they board about one in every 20 flights.
Although the Federal Air Marshals admit they have never knowingly stopped a terrorist, there's no way of knowing how many possible attacks they may have deterred.