After two failed tries, an unarmed, unmanned aircraft expected to be the first to patrol the U.S.-Canada border has completed a flight from Arizona to North Dakota.

U.S. Customs and Border Protection officials said the Predator B drone touched down Saturday at the Grand Forks Air Force Base after a six-hour flight from Libby Army Airfield in Sierra Vista, Ariz.

"The aviators all brag about the perfect landing," said Michael Corcoran, deputy director for air operations at U.S. Customs and Border Protection's Air and Marine office in Grand Forks. "I guess we'll brag about this one, as well," he said.

Unmanned aerial vehicles, such as the one pictured here, are soon to be deployed along the Canada-U.S. border. (Gerald L. Nino/U.S. Customs and Border Protection) The drone is to be deployed along the Canada-U.S. border in January, with flights originating from the Grand Forks base.

Officials were waiting for clearance on air space before deciding on a schedule, Corcoran said.

An earlier flight on Thursday was cancelled because of maintenance problems, and a flight Friday was aborted because of poor weather.

The Predator weighs 4.5 tonnes, has a 20-metre wingspan and can fly undetected as high as 15,240 metres. It can fly for 28 hours at a time, and will be equipped with sensors and radar.

The drone has been in use along the southern border with Mexico since 2005.

Vital to protect borders, senator says

Senator Kent Conrad, a North Dakota Democrat, said the state's congressional delegation had been working for four years to get the unmanned aircraft to North Dakota.

"It is vital to America's security that we protect our borders, particularly the northern border," Conrad said. "The Grand Forks Air Branch plays an essential role in helping shut the door on terrorists who want to sneak across remote border points to strike on U.S. soil."

Along the entire Canada-U.S. border, United States Customs and Border Protection agents make about 4,000 arrests and intercept about 18 tonnes of illegal drugs each year, officials say.

It is expected the flights from Grand Forks will patrol a 500-kilometre stretch of border between Manitoba, North Dakota and Minnesota.

Some experts have questioned the safety of unmanned planes.

In 2006, a Predator patrolling the southern border crashed near Nogales, Ariz. No one was hurt and no property was damaged, but the plane narrowly missed a house.