Sources say a bomb threat aboard a Vancouver-bound Cathay jetliner has turned out to be a false alarm.

National Defence scrambled two CF-18 fighter jets from CFB Comox toward the flight Saturday afternoon after a bomb threat was made.

Cathay Pacific flight number 839 was en route from Hong Kong. Sources told CTV News that two threats were called in from a payphone in Vancouver from someone who said there was a bomb on an outgoing Hong Kong-Vancouver Cathay Pacific flight.

Authorities immediately dispatched the fighter jets to escort the plane into Vancouver International Airport along its scheduled flight path.

The plane landed without incident at around 1:35 p.m. local time but once it hit the tarmac, investigators with sniffing dogs screened the plane and luggage aboard the flight thoroughly.

Authorities also screened passengers waiting at the Vancouver airport to board the same Cathay Pacific plane back to Hong Kong overnight Saturday. Passengers and their luggage were reportedly cleared for travel.

Police now believe the bomb threats were made as a crank call, according to sources.

"This threat is being taken very seriously," said RCMP Cpl. Sherrdean Turley. "We just want to ensure the travelling public that there is no threat at this time."

Investigators found "nothing of concern" on board, she told reporters outside Vancouver International Airport.

"The RCMP investigation will be continuing and hopefully we'll find out exactly what happened," she added.

No one has been arrested in connection with the incident.

Turley said the threats were phoned into the Richmond, B.C. RCMP at 10:43 a.m. local time.

Passengers unaware of threat

Several passengers told CTV BC reporter Michele Brunoro that they were not told about the security threat during the flight.

"No announcements were made on board," she said. "Some passengers noticed the fighter jets out the window and were frightened. But there was no panic on the plane. Everyone remained calm because passengers had no idea what was going on."

There were 283 passengers and 14 crew members on board. Passengers were allowed to leave the airport about four hours after landing on the tarmac.

"I was scared," said one passenger about the moment he noticed the fighter jet outside the plane's window. "It was flying very near to our plane."

A Vancouver Island resident who witnesses the escorted plane fly by said he was able to snap about 20 pictures as the aircraft made its way across the horizon.

"I just heard planes overhead, looked up and saw a big aircraft with a fighter right on its wings," said Patrick Beaton in a telephone chat with News Channel. "At a distance behind was another fighter jet. It was pretty impressive to see."

Major Holly Apostoliuk, a public affairs spokesperson for NORAD, would not say how long it took the fighter jets to reach the aircraft.

"At any point we can have the aircraft on the ground or airborne to respond to any threats that may occur," she told CTV News Channel Saturday evening.

Alan Bell, a terrorism expert, told CTV News Channel that regardless of the scenario, fighter jets are always deployed when there is a credible threat to public safety.

"We don't know yet what the threat was but each situation scenario would have elicited a response from military aircraft...until the aircraft is safely on the ground," he said.

The fighter jets would be ordered to shoot the plane down if terrorists took over the plane's cockpit and aimed the plane towards a residential area, he added.

With files from CTV's Ottawa Bureau Chief Robert Fife