The Sikorsky UH-60-A Black Hawk is one of seven aircraft assigned to the Department of Homeland Security to patrol the Canadian border, an increasing security concern for a government determined to prevent another terrorist attack.

He's responsible for what's called the Havre Sector.

That's a somewhat deceptive name since it's a 400,000-square-mile swath of territory that runs along the Canadian border from North Dakota to the Continental Divide and south to the borders of Arizona and New Mexico.

Its main focus, however, is 456 miles of the largely open Canadian border, which is where the Black Hawk is headed on this day.

At about 800 feet off the ground, the 12,000 pound chopper thunders along with three crew members and three passengers at about 175 mph, spooking herds of skittish antelope in the stubblefields below. Both 1,200-horsepower engines suck in about 120 gallons of fuel an hour. The Black Hawk can carry enough fuel, about 10,000 pounds, to remain aloft for 4 1/2 hours.

"This cruises at about 145 knots (167 mph), which is enough for us to keep up with most single-engine aircraft," said co-pilot Chris McGilvra.

Its home base in Great Falls makes it easier to intercept unauthorized aircraft heading into the United States from Canada.

"That does happen, but they're generally legitimate people who filed faulty flight plans," Blackburn said. "It's the guys who are flying under the radar who are our greater concern. That's why we have interceptor aircraft with advanced surveillance systems to pick them up."

In addition to the two Black Hawks and a smaller Astar helicopter, the air wing has two Citation C-550 II all-weather tactical jets capable of flying 358 knots (about 414 mph) that are used as interceptors. They're equipped with a sophisticated radar system and an infrared detection system.

"This plane is amazingly quick and quiet," said Hank Jones, operations chief for the air branch. It also can slow down to tail smaller planes from a distance, tracking them with fire-control radar, which is a long-range surveillance system similar to that in F-16 fighter jets.

"That's the radar that locks a target in so the F-16 can shoot it," Lindsay said. "But that's not our intent. We just want to lock it in long enough that we can get another aircraft in to deal with it."

The air wing also has a Pilatus PC-12, which is a single-engine turbo-prop aircraft useful for transporting ground crews and equipment, and a Cessna 206 surveillance plane.

Lindsay estimated that the aircraft are valued at a combined $90 million.

Separated by a fence

When the Black Hawk reaches the Sweet Grass border station, it circles the small building sitting all alone in the vast prairie, then heads westward along the Canadian border.

Separating the two nations is basically a barbed-wire fence headed, as far as the eye can see, toward the Rocky Mountains in Glacier National Park. Every few miles, it's marked by a small white obelisk, but other than that, it looks to have been put up by farmers to keep their cattle at home.

"This border can be difficult to tell," McGilvra says as he flies over it. "There's a fence here, but you have to be right on top of it to see it. It looks like a fence separating two farms, so we have to rely on maps to verify it."

The Black Hawk flies over one blacktop road with no border guards. Alex Harrington, public affairs specialist for the U.S. Customs and Border Protection in Havre, notes that some crossings have been equipped with motion detectors that alert on-the-ground Customs and Border agents.

"We basically monitor the whole border," McGilvra says. "We search known spots that have had traffic before, areas that they have brought stuff in, plus areas that have the potential for stuff to be brought in."

As noisy as the chopper is, it would seem that smugglers would have plenty of time to run or hide.

"This Black Hawk creates a presence," McGilvra says. "But with a 20-knot wind and a low altitude, we can probably get pretty close to them before they spot us."

The chopper crosses the beginnings of the Milk River and gunner Todd Cox notes that a number of roads converge there. It is an area surveillance aircraft pay particular attention to.

"We're looking for the tracks of vehicles driving off-road," Cox says.

"We've got a truck to the left," McGilvra says. "But it looks like he's just checking his herd. We usually fly over those trucks to make sure they have the stuff that ranchers usually have, but we don't want to impede their operations."

Armed with HK416 assault rifles that can fire 700 to 900 rounds per minute, pilots also can set the Black Hawk down to check out suspicious operations. Cox says they recently spotted armed men on ATVs on the other side of the border and stopped to check them out — they were Canadian Customs agents.

Glacier National Park

Chief Mountain looms ahead of the Black Hawk. It's an imposing monolith towering above the prairie, capped with snow and surrounded by an apron of aspen and larch trees, gleaming yellow and orange in the midday sun.

The mountain marks the northeastern edge of Glacier National Park and a shift in surveillance tactics.

"We're working with the park to maintain its integrity," Jones says. "A Black Hawk is pretty noisy, so our eyes (there) are up high and quiet. The surveillance package of our Citations is amazingly sophisticated and quiet, allowing us to see without being seen. That makes it great for watching intruders and poachers in the park."

The air crews supplement more than 90 Customs and Border agents on the ground, including several who patrol the border on foot, weather permitting.

"Most of our agents are on the border," Harrington said. "They use vehicles, ATVs and snowmobiles. We also have three K-9 units."

The Black Hawk's rotors make a whump-whump-whump sound as the helicopter moves south across the Blackfeet Indian Reservation, and the crew remains alert for potential problems.

"This area is a huge concern to us with no radar," McGilvra says. "Our main concern is the border, but there's really no other agency to patrol the interior, so we do that, too."

Customs and Border Patrol agents join the pilots in the Black Hawk for those missions.

"We can put an entire SWAT team back there," Jones says. "We're unique among federal agencies because we're the only unit outside of the military with Black Hawks."

First anniversary

The Montana Air Wing, which recently marked its first year of service, is housed in new administrative headquarters between Holman Aviation and FedEx on Gore Hill, with a beautiful view of the city and the Highwood Mountains in the background. Large back-to-back heated hangers house its aircraft.