Canadian airlines are starting to feel the financial impact of a recent string of false threats, after several flights were diverted due to bomb threats in the last week.

The latest incident occurred Thursday on a WestJet flight headed to Victoria, B.C., from Las Vegas.

A bomb threat was called in around 4:20 p.m., and though the threat is not being treated as credible, the aircraft was being screened tonight by bomb-sniffing dogs. As of about 7 p.m. local time, those on the flight were being held in customs until the situation was resolved.

Before Thursday, four WestJet flights and one Air Canada flight were also recently diverted due to threats made against them, creating lengthy delays while police evacuated the planes to check for bombs. No explosives were found in any of the incidents, but experts say the scares still come with a hefty price.

Former FBI investigator Brad Garrett says each false threat can cost the affected airline “several thousands of dollars,” while also using up valuable police time and manpower. He says those expenditures are unavoidable, as airlines and police are required to respond to any and all threats made against airplanes.

“Unfortunately that takes manpower and money,” Garrett told CTV’s Canada AM on Thursday. “It’s a heavy weight both for the airlines, financially… and for law enforcement.”

However, he says most pranksters are eventually brought to justice, though the process can take some time. Investigators are usually able to trace a caller’s phone number, even if it uses a number-faking program. They’re also quite adept at tracking down email threats, and linking multiple threats together when a single suspect is behind them.

“You look at the wording of the threat,” he said. “Are they similar? Do they ask for the same demands?”

Garrett said, in most cases, bomb threats tend to come from either disgruntled former employees or passengers with a grudge against the airline. He says the threats are meant to disrupt business, but the people behind the threat often get a “thrill” out of seeing the fallout of the threat on television.

“That’s very stimulating for some people,” Garrett said.

Garrett says bomb threats are an ongoing problem, but those who make them are usually caught and brought to justice.

On Wednesday night, a Vancouver-to-Toronto WestJet flight diverted to Calgary due to a bomb threat.

The day before, a WestJet plane in Saskatoon was delayed for a bomb threat investigation.

On Monday, six passengers suffered minor injuries while evacuating from a WestJet flight that was forced to stop over in Winnipeg, en route from Edmonton to Toronto.

Another flight out of Edmonton was forced to land in Saskatoon on Saturday due to a threat.

And finally, the St. John’s International Airport temporarily closed down last Thursday after a threatening note was found in the washroom of an Air Canada plane.