The map of the continental United States is jammed with a constellation of multicolored dots. With a few computer mouse clicks, the image zooms in on a stretch of coastal California.

The screen shows the movements of dozens of aircraft: an American Airlines flight on a cross-country route. A recreational pilot enjoying a day off in his Piper Cub. A military helicopter on a training mission.

If something flies west of the Mississippi River, the Western Air Defense Sector is watching. Tens of thousands of aircraft daily move through the airspace of WADS.

The unit operates 24 hours a day out of a three-story building at McChord Air Force Base. It is comprised mostly of Washington Air National Guardsmen and members of the American and Canadian militaries.

In a room filled with four rows of computers, technicians gaze at screens, watch for intruders and respond to possible threats, sometimes by deploying F-16 fighter jets.

The importance of intercepting threats was hammered home more than seven years ago, when four teams of hijackers turned passenger jets into missiles and altered the nation’s history.

WADS’ workload has changed radically since the Sept. 11 attacks. Its jurisdiction has expanded eastward to include more than 70 percent of the continental United States. It now watches the interior of the country as well as the coastline and borders.

And it is doing so with fewer personnel – a worrisome trend for such an important mission, its commander said in an interview earlier this month.

“We can do sustained day-to-day operations,” Air National Guard Col. Paul Gruver said, “but I’m more challenged now than I was on 9/11.”

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