A Denver-bound United Airlines flight was diverted Sunday after two passengers got into a tiff. The cause of their argument? The Knee Defender, a $22 device that prevents an airplane seat from reclining and was invented right here in the District. Ira Goldman used to travel 100,000 miles a year for his trade policy work, which wasn’t always comfortable for his 6’3” frame. So in 2003, the Mount Pleasant resident created the tiny gadgets, which connect to a tray table.

Is this the first Knee Defender fight you’ve heard about?
Look, the product has been on the market for 11 years, and if this had happened before, I would know about it. On every Knee Defender, it says, “Listen to the flight crew.” If a flight attendant says don’t use it, you don’t use it. No matter what you’re using on an airplane, don’t get into a fight over it.

How many have you sold?
A lot. It keeps the lights on for my company. And we don’t advertise. It’s all demand-driven. A lot of people use it because laptop screens can crack when people recline suddenly. Knee Defender protects against that. It’s been working for people for a long time. A lot of people say, “I didn’t want to buy it. But I had to.”

What else have you invented?
There’s the Scanner Bag. Guys don’t have pocketbooks or purses, so they put their cell phone, wallet and keys in a basket when they go through security, then they forget it when they run to a flight. So this is a luggage tag with a pouch that let’s you keep it all attached. I’m a typical inventor — I see a problem and I think about what it would take to solve the problem. I used to do that by writing legislation. Now I do it with products for consumers.

What else are you working on?
I have a new kind of leash for a dog, so people can ride a bike while walking a dog safely. But there isn’t a big market for that. And I came up with a little thing that attaches a cup holder to rolling luggage, so your cup of coffee won’t spill. I decided the market wasn’t there. It looks funny to see the cup swinging back and forth.

How did you start inventing?
My dad was in the toy business, and I invented some toys for him. Before I was born, he invented a water pistol with a knob, so you look like you’re aiming one way but then it shoots sideways. At one point, that was on Super Soakers. My brother invented Phlat Ball — you throw it like a Frisbee and it turns into a ball.

Any D.C.-specific problems you’re thinking about tackling?
I think all bike lanes should be in the center of the street, so you don’t need to worry about car doors.

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