If you're hoping to nab the contentious Knee Defender to protect your legroom on your next international flight, think again: the seat-jamming device is prohibited by Canada's two major airlines.

Air Canada and WestJet say the seat-locking Knee Defender is not allowed on their flights.

Calgary, Alta.-based WestJet specifically names the Knee Defender on its list of unapproved carryon items. "You are not permitted to attach any unapproved device to any part of your seat or any other part of the aircraft," the WestJet website says. "Some examples of unapproved devices include knee defenders, seat belt extensions and booster seats."

The Knee Defender is also prohibited on Air Canada flights, an airline spokesperson said.

However, it hasn't been officially outlawed by Transport Canada or the Federal Aviation Administration in the United States. Both organizations say they leave that up to the airlines to determine.

What is the Knee Defender?

The Knee Defender is a little clamp that attaches to an airline seat's tray table, jamming the mechanism on the seat in front and preventing the passenger sitting there from leaning back. The $22 tool is marketed online as a way to protect your legroom on an airplane.

On Sunday, a United Airlines flight diverted from its destination to make an unscheduled landing after two passengers got into a heated argument over use of the Knee Defender.

A man had used the device to jam the seat in front of him, locking it in the upright position. The woman sitting in the seat didn't like that, so she called a flight attendant.

When the flight attendant asked the man to remove the device, he refused. The woman sitting in front then threw a cup of water at him.

The Newark-to-Denver flight landed in Chicago to kick both passengers off the plane. No charges were laid against the passengers, and Chicago police dismissed the case as a "customer service issue."

United Airlines prohibits the use of the Knee Defender. It's also prohibited on most other major American airlines.

Inventor speaks out

Knee Defender inventor Ira Goldman says the United Airlines incident is the first he's heard of in the 11 years since he invented the device. "Knee Defenders aren't about getting more space," he told CTV News Channel. "They're about stopping somebody from moving and hitting you."

He added that people should still be polite about how they use the device. "Start the conversation before there's a problem," he said.