A Sunwing Airlines pilot's "misunderstanding" set off a massive emergency response to a bomb threat near Pearson International Airport that forced the evacuation of two buildings and the dispatch of Toronto police's Chemical, Biological, Radiological, Nuclear, and Explosive Unit — an elite team that responds to suspected acts of terrorism.

Shortly after 9 a.m. on Sunday, Nov. 13, 2016, Toronto police received an emergency call after a Sunwing pilot discovered what he feared might be some sort of explosive device stuffed into his internal company mailbox.

When CBC Toronto called Sunwing about the incident, an employee who would only identify himself as Matthew described the device as "an antique radio battery." He said it was left for the pilot by one of his colleagues in what another employee described as a "joke."

The unidentified employee said the pilot thought "it would be cool" to put the battery in a colleague's mailbox.

Two large industrial buildings used by hundreds of Sunwing employees on Fasken Drive, near Pearson airport, had to be evacuated as police cordoned off the area. Toronto police also called in their CBRN unit — essentially a group of officers trained to deal with chemical, nuclear or bomb threats. Eventually, those officers determined the device wasn't a threat.

At the time of the November incident at Sunwing's Toronto offices, there was no mention Sunwing employees were involved.

'This was a misunderstanding'

In an emailed statement to CBC Toronto, Janine Massey of Sunwing said: "We can confirm that on Nov. 13 one of our pilots arrived at the Sunwing Airlines office and found an old radio battery in his mailbox. As he didn't recognize it and there was no note attached to it, he escalated the matter out of an abundance of caution.

"The authorities were notified, and in the interests of public safety, they dispatched their unit which handles hazardous materials and explosives. After investigating the scene, they were satisfied that this was the result of a misunderstanding between the pilot who left the battery and the pilot who found it."

Massey declined to answer if the pilot who left the device did so as a joke, or if the pilot has been disciplined.

Toronto police bomb squad was dispatched on Nov. 13, 2016 to investigate what turned out to be an old radio battery.

It's not clear how much the significant police response cost. Const. Caroline de Kloet, spokeswoman for the Toronto Police Service, confirmed the incident occurred, saying: "but no charges were laid. The complainant did not want to press charges."

While there's no indication the incident was an act of malice, it's another bizarre situation involving the airline's pilots. Last weekend, Calgary police said Sunwing pilot Miroslav Gronych boarded a Sunwing Airlines 737-800 series aircraft shortly before 7 a.m. local time on Saturday while under the influence of alcohol.

He was arrested on Saturday and charged with having care and control of an aircraft while impaired and having care and control of an aircraft with a blood alcohol level over .08.

The plane was scheduled to make stops in Regina and Winnipeg before continuing on to Cancun, Mexico. It had 99 passengers and six crew members on board.

Members of the flight crew noticed the pilot was behaving oddly before he passed out in the cockpit, according to police.

Calgary incident leads to federal concern

The Calgary incident has prompted Federal Transport Minister Marc Garneau to write a letter to all commercial air carriers, asking the airlines to get in touch with Transport Canada to outline and confirm their safety protocols by Feb. 15.

"The incident in Calgary reminds us all of the need to ensure that protocols are up to date and that they are being implemented with all the required resources, including measures designed to confirm pilots' fitness to fly," Garneau wrote.

He also said in the letter that Transport Canada is also planning a workshop in early spring where airlines, unions and medical experts can get together to "consider further steps necessary to enhance aviation safety."