All domestic and international flights have been grounded as a precautionary measure after a series of attacks on high-profile targets in the United States. Only military, police or humanitarian flights are permitted to fly.

The United States Federal Aviation Authority ordered all international flights to the United States to be diverted to the nearest airport. There were close to 500 aircraft affected. About 250 returned to their point of departure, while Canada received close to 200 rerouted planes.

Airports throughout Atlantic Canada have already received dozens of flights including Moncton, St. John's, Halifax, Goose Bay, Stephenville, Montreal, Ottawa, Toronto, Hamilton, Winnipeg, Edmonton, Calgary, Abbotsford and Whitehorse.

Halifax airport says they currently have 44 planes on the ground and about 7,000 to 8,000 passengers. The RCMP is sweeping all of the planes and the passengers' luggage after which they will be transported to large sports facilities in the city for the night.

The RCMP originally said it would take up to 90 minutes to sweep each plane and process passengers, but the enormous size of the effort has sped up the process. Four planes are now being emptied each hour. Officials say everyone should be off the planes by 5 a.m. ET.

Some weary-looking passengers leaving the planes were just happy they were safe.

"We're alive, we're safe, our prayers go out to the other people," said Matthew Sakalski of Florida.

Newfoundland expects to host anywhere from 10,000 to 15,000 people in St. John's, Gander and Stephenville. St. John's airport is operating at double capacity with 27 wide-body jets sitting on the tarmac.

They will be put up in hotels, conference centres and private homes. Officials in Gander say they've had a tremendous response from people living in the area.

"People are coming in with blankets and water and walking into the office volunteering their time," said Maj. Alfred Richardson.

Many people in Toronto are also offering their homes to travellers stranded at Pearson Airport.

"All Canadian airspace has been closed other than for inbound overseas flights," said Calgary Airport Authority spokesperson Mike Cunnington.

Aviation officials in Whitehorse had a false alarm after a South Korean 747 was intercepted over Alaska and escorted to the airport by U.S. and Canadian jet fighters.

Officials believed it could have been a hijacked aircraft, but it turned out to be a redirected airliner running low on fuel.

Jet fighters circled Whitehorse as the plane was inspected.

Prime Minister Jean Chretien has condemned what he called a "cowardly attack" south of the border and pledged full assistance to the U.S., including medical support and a home for the displaced travellers. He also assured Canadians to remain calm, noting that the government was increasing security.

Written by CBC News Online staff