DENVER (CBS4) – The inventor of a plastic gadget that prevents airline seats from reclining fired back at critics Tuesday.

His device, called the Knee Defender, stoked tempers between two passengers Sunday and forced a plane bound for Denver International Airport to divert to Chicago’s O’Hare International Airport.

According to United Airlines, a man used the Knee Defender to the seat in front of him to prevent it from reclining. Two clips on the device attach to a seat-back tray and keep the passenger in front from shifting the seat back. The woman sitting in front of him insisted he remove it — and so did a flight attendant — but he refused. The other passenger then threw water in his face.

Both passengers were sitting in a section of the plane with four extra inches of leg space per seat.

The inventor said he created it because he was uncomfortable on planes. The device costs $21.95.

“I would sit down in the plane and I’d get smacked in the knees by the person reclining,” Ira Goldman told CBS4. “The product’s been on the market for 11 years. This has never happened before.”

Goldman says the Knee Defender comes with instructions that tell the owner to be courteous to fellow passengers and to listen to flight crew.

“What really escalated this was the woman who threw a cup of water in the guy’s face,” he said. “I don’t know if anybody is calling cup manufacturers today, but they’re certainly calling me.”

Goldman said airlines should consider installing seat bottoms that move forward rather than seats backs that recline — if passengers really want to lean back.

The FAA said the devices can be used at the discretion of each airline. United said in a statement that it doesn’t allow devices that prevent seats from reclining.

Denver residents who spoke with CBS4 about the incident likened it to road rage:

“It’s more about really reacting rather than thinking it through,” one woman said.

“It’s never a pleasure to fly on the airlines any more. And I’ve grown accustomed to it,” another added.

“I think it’s an interesting testimonial of our times,” a man said.