It’s an early weekday afternoon at the Flight 23 store — a new boutique on 34th Street that sells nothing but Nike’s Jordan Brand gear — and the kids are flooding in. Most are in their late teens and early 20s and look pretty similar from the ankles up. Many wear hoodies. Jeans. A few have large headphones over their ears or slung around their neck.

From the ankles down, though, is where it gets interesting. One guy’s got red high-tops so shiny they’re almost metallic, and another’s got a pair splashed with colors almost like a Jackson Pollock painting. Both pairs are completely pristine.

The Jordan fans have come to Flight 23 to browse the shoes displayed on the back wall like museum pieces, and maybe pick up a new pair, assuming they’ve got $150 burning a hole in their pocket.

For many sneakerheads, Air Jordans are clearly the kicks of choice. Never mind the fact that most of these customers weren’t alive when Jordan laced up his signature shoes for the first time — 30 years ago, during his rookie Chicago Bulls season. And never mind that they weren’t even out of diapers when His Airness took his final NBA jump shot in 2003. It’s Air Jordans they want.

It’s not an overstatement to say that the Air Jordans are the most influential sneakers ever created.

They made “Nike the dominant brand in basketball, redefine[d] the footwear industry, and, thanks to aggressive ‘retro-ing,’ still sell literally millions of shoes every year,” Ben Osborne writes in his new book “SLAM Kicks: Basketball Sneakers That Changed the Game.”

In a strange twist, sales of the sneakers have exploded since Jordan retired. Nike has released a new version every year since 1985, and the company is now on model XX8. The XX9s launch in the fall, with no end in sight. Jordan is probably going to be levitating around the retirement home in Version LXIs.

Nike’s Tinker Hatfield, who has designed numerous Air Jordan styles, recalled that when he was working on Xs, and Jordan retired for the first time (before returning three years later), Nike told Hatfield not to bother with the XIs.

“ ‘The whole thing was done, and Michael is not going to play anymore,’ they’d say,” Hatfield told Sole Collector. “We wouldn’t be able to sell shoes with his name on them. I, of course, didn’t stop, and didn’t believe it.”

Good thing Nike never pulled the plug. Last year in the US, Jordan’s shoe line was good for $2.5 billion, says Matt Powell, an analyst with SportsOneSource, a North Carolina research firm. The next largest player is LeBron James, who sold $300 million for Nike.

Jordan Brand shoe sales have nearly doubled since 2004, Powell says. That’s a huge surge for a product whose namesake has spent more time in recent years in divorce court than on the basketball court. (In 2006, His Airness split from first wife Juanita and paid her a whopping $168 million.)

“I think Jordan personifies the luxury brand. Conspicuous consumption is a lot of what drives sneaker sales,” Powell says. “It’s about saying, ‘I’ve got $180 and you don’t.’ ”

Nike also manipulates inventory, often releasing a limited supply of certain models, forcing fans to camp out in front of stores if they want to snag a pair.

Last year, releases of the Jordan XI Retro Gamma Blues were marred by long lines and fights reported in Dallas and the Bronx. In Ohio, a stampede of shoppers busted through a glass door at a Champs Sports to get their hands on the Air Jordan XII Retro “Taxi.”

“Nowadays it’s almost impossible to get them,” says Michael Tran, co-author of “Jordan Collectors’ Price Guide.” “If you try to get them online, they sell out in 10 seconds.”

The frenzy has led to a robust secondary market, where sellers can earn hundreds of dollars flipping the shoes on eBay.

It’s a far cry from the debut of Air Jordans three decades ago, when the first release found its way to the clearance racks. (An original pair is now worth $1,900.)

The irony of the story — and of Nike’s 30-year windfall — is that Jordan was dead-set on signing with Adidas when he came out of the University of North Carolina in 1984. He liked that Adidas sneakers were lower to the ground. The German company, however, was going through a transitional crisis at the time after the death of its founder, and was too disorganized to nab the future superstar.

Nike pitched Jordan using a highlight tape set to “Jump” by the Pointer Sisters. Jordan was offered $500,000 a year in cash for five years, which was $350,000 more than the next highest shoe contract, awarded to fellow Tar Heel James Worthy.

MJ laced up his red-and-black Air Jordan high-tops for the first time during the Bulls training camp, drawing some eye rolls from his teammates and the training staff. He first wore them on the court during an October 15, 1984, preseason game against the Knicks. (Chicago prevailed, with Jordan chipping in 21 points.)

Soon, however, Jordan’s footwear began to cause trouble. NBA commissioner David Stern ruled that the kicks violated the league’s dress code, and he slapped the rising star with a $5,000 fine for every game he wore them. Jordan would still continue to play in the shoes from time to time during his rookie season.

Sensing a marketing opportunity, Nike paid the fines on Jordan’s behalf and later produced a TV commercial, casting Jordan and his shoes as rebellious: “On October 15th, Nike created a revolutionary new basketball shoe. On October 18th, the NBA threw them out of the game. Fortunately, the NBA can’t keep you from wearing them.”

Air Jordan I’s hit shelves in March 1985, retailing for $65 — the most expensive sneaker on the market at the time. By May, Nike had sold $70 million worth, according to ESPN.

“Nobody expected the mass hysteria created by its release,” Jordan told the AP in 2008.

The next year, Nike released a radically redesigned sequel, removing the prominent Nike swoosh in favor of a cleaner look.

The Air Jordan III was the first to feature the now-iconic Jumpman logo. Nike designers had originally wanted to base Jordan’s personal logo on a photo they’d seen in Life magazine of the superstar soaring toward the basket, his legs outstretched in a V shape. When they were unable to secure the rights to the photo, they set out to recreate the pose in a studio.

“I wasn’t even dunking on that one,” Jordan told Hoop magazine in 1997. “I just stood on the floor, jumped up and spread my legs and they took the picture. I wasn’t even running. Actually, it was a ballet move where I jumped up and spread my legs.”

(Legend has it, UNC coach Dean Smith insisted that his players take ballet classes to improve flexibility.)

The sneakers quickly grew in popularity and began to make their way into pop culture. Jerry Seinfeld wore a pair in the second season of his TV show, as did a character in Spike Lee’s “Do the Right Thing.” In 1992’s “Batman Returns,” Michael Keaton donned a pair of Air Jordan VI’s painted black to look like boots.

The designs became more complex over the years, with subsequent shoes based on Jordan’s Porsche (he’s an avid car collector) and even an F-22 Raptor fighter plane.

But after Jordan retired for good in 2003, sales of his eponymous shoe began to falter. Nike hit on an ingenious solution to the problem: release retro versions of the classic Jordans, often in different colorways and styles.

“Nike has put out about 700 pairs of Air Jordans,” says price guide author Tran.

The growth in sales is coming from this market, as opposed to Nike moving millions of its new Air Jordan XX8. Re-releases of the I, V, VI, XI and XII are the most popular, Powell says.

The trend doesn’t seem in danger of petering out. Last year, for example, a single release of “Powder Blue” Air Jordan X racked up $35 million in sales in a single day. Jordan himself took home $90 million in 2013, according to Forbes. That should buy a lot of golf balls.

Kids love Mike’s sneakers — just not for playing ball

“It’s gotta be the shoes,” Spike Lee once said in a famous Nike spot from the 1980s. To find out exactly what draws devoted sneakerheads to Air Jordans, we stopped by the new Flight 23 store on 34th Street. The boutique, which is attached to FootAction, sells only Jordan Brand footwear and gear, and is the first and only one of its kind in New York City.

Most of the customers were young men in their teens and early 20s, who weren’t even out of diapers when His Airness was at his peak. No matter. Many confessed to liking Air Jordans because they had the most “hype.”

Here’s their take.

Sergio Rojas, 20, The Bronx

“[Says sarcastically] Michael Jordan was a basketball player? I don’t have memories of him playing. When I was younger, my parents used to buy me random shoes. I never had a chance to buy anything I liked. Now that I work and can buy shoes, I buy things that are more exclusive. I just love the shoes. [They] show who you are as a person. I don’t like to wear basic shoes.”

Albert Gloss, 18, The Bronx

“I wear Air Jordans for fashion. I don’t wear them for basketball. Can’t do that. They’re too special. I pay too much money for them. You gotta keep them clean, all day. I wear Kobes to play. Can’t do Air Jordans.”

Robert Abreu, 17, Manhattan

“I want [my Air Jordans] to look new all the time. I don’t play basketball in them. They’re more for style and dress. My friends wear them. Famous people wear Jordans all the time. Sometimes girls compliment me on them at school. They say, ‘Nice sneakers.’ ”

Jesse Rimland, 15, Manhattan

“I always liked shoes, and then I realized I could sell them and make money off of them. I got my first pair about five years ago. I have 15 pairs now. I don’t remember Jordan playing. He’s not one of my favorite players, but I like his sneakers. My favorite player is Carmelo Anthony. My advice for the Knicks? Defense.”