JOINT BASE LEWIS-MCCHORD, Wash. -- Inside a windowless, three-story building with thick concrete walls, past a heavy metal door with a sign that says, "WARNING. Restricted Area ... Use of deadly force authorized," on this recent afternoon you can find Airman 1st Class Juliana D'Aprile, who is all of 20 years old.
Sitting in front of a bank of flat-screen monitors at the control center of the Western Air Defense Sector that combine information from 172 radar sites, she literally would be the first to spot a hijacked or terrorist plane.
The sector doesn't make the news unless it's a story about a sonic boom created by a jet scrambled to intercept a potential threat.
"Our measure of success is that nothing happens," said Col. Paul Gruver, commander of the sector.
Since the Sept. 11 attacks, no terrorist planes have done anything in the United States, perhaps because they, too, are aware of how they could be tracked since the radar system was dramatically changed after the tragedy.
In this world, D'Aprile spends her days looking at screens full of moving dashes and dots and streaks in bright white, green, purple, red.
Given how much she has to focus, she sits in front of the monitors for an hour, then does other work, then returns for another hour, a typical shift to keep them sharp for those doing this kind of work at the sector.
"It's always exciting," said D'Aprile, a tracking technician with the Washington Air National Guard, as she zoomed in on a plane about to cross into the United States through Texas. "I want to know if this is a friend. I want to know who this guy is."
The Western Air Defense Sector covers three-quarters of the country -- everything west of the Mississippi River. That's 3,300 miles of border.
The sector has 230 military members. At any one time, a little more than two dozen technicians and officers are in that control room.
D'Aprile is among the first line of technicians who assess the radar blips. Behind her is an array of other technicians and officers, eventually leading to a weapons section for scrambling jets.
It used to be, back in the Cold War days, that we worried about Russian bombers and nuclear missiles coming across the Arctic.
That's why the United States and Canada created NORAD, which stands for the North American Aerospace Defense Command. Canadian military personnel also work at the Lewis-McChord air-defense control room.
The system was depicted in movies such as 1964's "Dr. Strangelove" and 1983's "WarGames," with a young Matthew Broderick hacking into NORAD computers.
But those days are gone.
NORAD this year even conducted a joint exercise with the Russian Federation Air Force in responding to a simulated hijacking of a plane en route to the Far East.
When 9/11 happened, the agency made drastic changes to its radar tracking.
A slide it shows graphically depicts its radar coverage before that day: It was all at our borders, using military radar; the inside of the country was pretty much void. Its computers now combine Federal Aviation Administration radar, and the country is blanketed.
To keep its edge, he says, the sector regularly runs various exercises.
These range from scrambling jets in a make-believe terrorist scenario to having technicians track planes while simultaneously dealing with computer failures and even a co-worker having a heart attack.
At some point, in a decision that has to be made in minutes, if not seconds, fighter jets will be have to be scrambled.
At the Western Air Defense Sector, that happened 179 times in 2009.
One such scramble took place on Aug. 17, 2010, when a pair of F-15 jets caused two loud sonic booms over the Seattle area.
The military jets were pursuing a seaplane that breached a 10-mile restricted zone when President Barack Obama visited the city.
The plane landed in Lake Washington, and photos show a chagrined-looking pilot at the dock after talking to Secret Service agents. The plane had been flying from Lake Chelan to Seattle, and the pilot apparently hadn't checked air-restriction notices.
Something that the fighter pilots can do that the radar can't is fly right next to the unidentified plane and look directly at its pilot.
"My billion-dollar system is very good at telling me where they've been, but it tells me nothing about what's inside that person's head," Gruver said.
At the control center, D'Aprile continues looking at the blips on her monitor, making decisions about whether that digital signal is a friend or a potential foe.
"It's hard to explain what you do to friends and family," D'Aprile said. "But what you're doing is protecting the U.S."
(Distributed by Scripps Howard News Service, www.scrippsnews.com)