Correction: An earlier version of the story incorrectly said this year is the first time since 2011 that the TSA academy has welcomed new trainees. Training for new groups of federal marshals began in 2016. The story also misstated the average salary for air marshals: $44,000 is the median starting base salary. This version has been corrected.

Future federal air marshals participate in a shooting exercise inside one of the shooting houses at the William J. Hughes FAA Technical Center's Federal Air Marshal Service Training Center on the campus of the Atlantic City International Airport in Egg Harbor Township, N.J. (Astrid Riecken/For The Washington Post)

The first thing you notice is the gunfire. Loud blasts slice through the air with a sharp crack, crack, crack.

Over the course of a day, the recruits who come to this tree-studded campus will shoot hundreds of rounds from every position. Lying, kneeling, standing, sitting — on the move and standing still. Then they’ll come back the next day and shoot hundreds more. By the time their training is complete, they’ll have fired close to 5,000 rounds.

That’s because when you’re a federal air marshal and your work takes place in a 20-foot-wide space, 30,000 feet in the air, precision matters.

Air marshal trainees will go through a 16-week course designed to teach them how to spot – and thrwart – potential threats on the thousands of commercial air flights that crisscross the globe each day. This group is among the first new recruit classes since 2011.

They’ll spend eight weeks in New Mexico learning basic police techniques before coming to this special Transportation Security Administration school in Atlantic City where their training takes into account their role as armed, undercover agents who spend the bulk of their time aboard commercial planes.

A terrorist attack inside a remake of a commercial Boeing 767 passenger airplane is simulated during a training practice. (Astrid Riecken/For The Washington Post)

Shooting — and shooting with precision — is a big part of that, but so is being able to blend in and quietly size up passengers to determine who might be a threat. The Federal Air Marshal Service’s motto? Invisus, Inauditus, Impavidus (Unseen, Unheard, Unafraid).

Their charge is straight­forward.

“Our focus in life is to make sure another 9/11 never happens,” said Michael LaFrance, assistant supervisory air marshal in charge at the Transportation Security Administration’s Atlantic City training center.

It’s not clear whether the Trump administration’s efforts to more closely monitor potential terrorists trying to come to the United States aboard commercial aircraft will mean a greater role for air marshals — or an expansion of their ranks.

Two of the president’s executive orders — which are tied up in federal court — prohibit people from several Muslim-majority countries from entering the United States. The administration also recently barred passengers traveling from airports in several Muslim-majority countries from bringing laptops, tablets and other portable electronic devices on board with them when they fly, amid concerns that such devices could be used as bombs.

A remake of a terminal at Reagan Washington National Airport is set up to train future federal air marshals at the William J. Hughes FAA Technical Center's Federal Air Marshal Service Training Center on the campus of the Atlantic City International Airport. (Astrid Riecken/For The Washington Post)

But the president also has proposed eliminating a $57 million program that uses air marshals and other law enforcement personnel to conduct random sweeps of airports, subway stations and other high-profile public facilities to guard against terrorist attacks.

Here in New Jersey, however, instructors and administrators have tuned much of that out. They are focused on training.

President John F. Kennedy created the air marshal program in 1961, after international hijackings raised concerns about the safety of commercial air travel. But it remained relatively small. At the time of the Sept. 11, 2001, terrorist attacks, there were 33 air marshals. The program’s total budget: $4 million.

But after 9/11, everything changed. The Air Marshal Service underwent a massive expansion, adding thousands of new officers.

Though TSA officials decline to discuss specific numbers citing security concerns, a 2016 report by the Government Accountability Office said the TSA employs “thousands” of air marshals. In fiscal 2012, its annual budget was $908 million. But in the intervening years, the Air Marshal Service has weathered its share of cuts and questions about how it deploys its people since there are not enough marshals to cover every flight.

The 2016 GAO report offered recommendations on how the TSA could improve its deployment strategy, and officials at the agency have moved to incorporate those suggestions. There have also been concerns about employee morale among marshals given the rigors of the job and relative low pay; the median base starting salary is $44,000. About 7 percent of the marshals are women.

Thomas Kelly, a spokesman for the service, said every effort is made to help air marshals manage the pressures of the job and the stress that comes with the rigors of their travel schedules.

Once they complete basic police training at a facility in Artesia, N.M., they are sent to Atlantic City, where the focus shifts to more tailored instruction. They spend time in gyms where they punch, jab and kick “body opponent bags” — large rust-orange-colored dummies mounted on flexible metal stands. They also take part in simulated hijackings staged aboard true-to-life models of the types of aircraft cabins they are likely to fly.

In short, this is not a place where people spend a lot of time sitting behind a desk.

The goal, LaFrance said, is to place trainees in real-life situations that will sharpen their instincts for sussing out trouble. Rookie air marshals need to know how to size up a situation quickly but not overthink it, he said. The job also requires them to blend in — just another weary traveler trying to get to his or her destination.

Even so there are special considerations.

“Fighting someone on an aircraft is like fighting someone in a phone booth,” said Cardo Urso, a former Marine who teaches close combat techniques as part of the school’s defensive measures course. “There is very little room for error.”

Standing in a large training room at the campus about 10 miles north of Atlantic City’s famous boardwalk, Urso outlined the three options air marshals face when confronted with a threat: fight, flight or freeze.

Of the three, he said, fight is the only option.

His course includes instruction in pressure points to cause pain or induce muscle spasms and other techniques that will disable an attacker quickly and with a minimum of fuss. He showed visitors a rubber knife designed to deliver a small shock, which he described as “a pain penalty for negative performance.”

At the training center, there is a high-ceilinged room designed to look like the waiting area of an airport. There’s a TSA screening area, a “Starbucks,” a “Dunkin’ Donuts” and the familiar black faux-leather seats arranged back-to-back in groups of eight — so common in U.S. airports. Those who regularly travel through Reagan National Airport would be amused to see familiar runways outside the “windows” of the concourse.

This is where some of the trainees’ most intensive training will take place. Recruits will be put through scenarios including hijackings in spaces designed exactly like the cabin of an aircraft. Actors are brought in to play passengers. Instructors are able to fill the cabin with smoke or shut off the lights. The encounters are recorded so that teachers can offer feedback. The curriculum includes at least 100 possible scenarios.

The training doesn’t end once the air marshals graduate. Every marshal is required to do 20 hours a year of follow-up training. Others may return to Atlantic City to train as instructors.

That’s what has happened in a far corner of the campus, home to three indoor shooting ranges, where the sound of gunfire punctuates the midmorning gloom.

Inside, about a dozen veteran air marshals, clad in khakis and black polo shirts, are fanned out in front of paper targets. They are training to be firearms instructors.

The floor in front of them is littered with shell casings. Expert marksmanship is a key requirement for air marshals, who are tested quarterly on their shooting skills. Daniel Kowal, a supervisory section chief for firearms training, said over the course of their training, air marshal candidates may shoot as many as 5,000 rounds — more than some police officers fire during their entire career.

Back on the floor, an instructor barks out another set of orders.

“This time we’re going to start in a kneeling position,” he tells the group. When the marshals are ready he gives them the signal to fire. The sounds is deafening. Their accuracy? Spot on.