The aircraft will be equipped with cutting-edge photographic surveillance and monitoring equipment to watch for any suspicious activity, a spokesman for Montana Republican Senator Conrad Burns said Friday. Matt Mackowiak said the beefed-up border security comes in the wake of the Sept. 11, 2001, terrorist attacks on the U.S.

"(Sept. 11) taught us a lot, and the northern border requires greater security and greater surveillance," Mackowiak said from Washington, D.C.

"I think the Congress, the administration and the American people are committed to making sure we are doing everything we can to protect America."

This is the third of five special surveillance units to open along the U.S. border with Canada. The air unit will be based in Great Falls, Mont.

Last year, Burns secured an $18-million US appropriation from the Department of Homeland Security for the Montana air unit, putting it ahead of schedule by one year. It's expected to start operations this summer.

The air border patrol is intended to provide a rapid response in the event of another terrorist attack, Mackowiak said.

Apart from terrorists, the aircraft will be used for drug enforcement and immigration control.

Mackowiak called it a win-win situation, saying increased border security benefits both countries.

But any time there is increased surveillance there are civil liberties and privacy concerns, he acknowledged.

"We are not trying to interrupt the honest flow of goods and services and commerce between Montana and Canada," Mackowiak said. "It's in everyone's interest to facilitate as much of that as possible."

Canadian officials had little comment about the U.S. plan.

"Canada recognizes that every country has the right to protect its borders," said Kara Prest, a spokeswoman for the Canada Border Services Agency.

The first surveillance unit was announced in 2004, and has been operating out of Bellingham in Washington state. Another unit opened in upstate New York, south of the border with Quebec.

Mackowiak said both of those units have intercepted large drug shipments and have made arrests.

The U.S. also plans to set up air border patrols in North Dakota and Michigan in the future.

The government operates similar patrols along the U.S.-Mexico border.