Nike cofounder Phil Knight almost wrote off the idea of filling running shoes with air as 'comic book stuff' - until he heard how Adidas had reacted to the pitch

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The Nike Air Jordan is one of the best-selling franchises of all time.

• Nike cofounder Phil Knight nearly dismissed the idea of air soles when an aerospace engineer presented it to him, he wrote in his memoir "Shoe Dog." 
• He thought the technology was "comic book stuff," but changed his mind when he learned Adidas thought the same.
• Nike's air soles are featured in some of the most popular sneakers and bestselling sneaker franchises of all time.
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Nike's famous air sole technology almost never came to fruition. 

In 1977, former aerospace engineer M. Frank Rudy approached Nike cofounder Phil Knight with an idea for "the Next Big Thing:" injecting air into a running shoe, Knight wrote in his memoir "Shoe Dog." 

While Rudy told Knight air soles would offer more cushioning and support, Knight was skeptical of the idea.

"Humans have been wearing shoes since the Ice Age, I said, and the underlying design hasn't changed all that much in forty thousand years," Knight wrote, adding that there hadn't been a breakthrough since the late 1800s. "It didn't seem all too likely that, at this late date in history, something so new, so revolutionary, was going to be dreamed up."

He added: "'Air shoes'" sounded to me like jet packs and moving sidewalks. Comic book stuff."

But all that changed when Knight found out Rudy had pitched Adidas and received the same reaction. Knight put the air soles in his running shoes and went for a six-mile run. 

"I ran back to the office," Knight wrote. "Still covered with sweat, I ran straight up to Strasser [Nike's director of marketing] and told him: 'I think we might have something here.'"

Read more: Nike designed a sneaker with a flared heel that looked like a water ski in the 1970s - and customers had a surprising reaction when the shoe was recalled for causing injuries

The design was first featured in Nike's Air Force 1 model, launched in 1982. It went on to become one of the most popular sneakers ever, and millions of pairs are still sold every year, Business Insider previously reported.

It's also a hallmark of the Air Jordan, launched in 1985 as part of an endorsement deal with Michael Jordan, one of Knight's biggest accomplishments. It's now one of the most successful sneaker franchises of all time.