Fast forward a few months and McDowell’s Florida nights were brought to the fore when he was briefed on the Foot Locker project, which, at the time, was named “Sky Air.” Once he heard that name, he started sketching different colored sunsets, dotted with palm trees that ranged from the artful to the geometric. From there was born the Air Max Plus’ instantly recognizable gradient upper and palm-tree inspired exoskeleton that wraps around the foot. McDowell’s nautical inspiration didn’t stop at the upper. One of the Plus’ most striking, albeit small, details was the presence of a shank that extends from the bottom of the sole to the midsole. It creates a division between the front and back Air units and gives the Plus a distinct look. Ironically, in France, the Plus is referred to as “la requin”—the shark shoe—but McDowell’s real inspiration was drawn from a whale’s tail.

Perhaps what makes the Air Max plus so striking is that seemingly simple design elements eschewed convention and protocol because of the designer’s relative inexperience. Take the Swoosh, for instance. It is one of the most recognizable logos in the history of design, let alone fashion. In 1997, however, McDowell wasn’t provided with a template for the logo. As a result, the Swoosh on the Air Max Plus is slimmer and longer than it should be, which has contributed to the shoe’s unique design and, consequently, its place in Nike lore. Because McDowell was new to Nike, he challenged certain conventions based on his own experience as a runner. “You learn to always run facing traffic so that cars can see you,” he explained, so he found it "weird [that] reflectivity [was put] on the back of almost every shoe when you need reflectivity all the way up the front.” On the Plus, McDowell added reflective bars on the tongue and toe box, which became one of the shoe’s distinguishing—and most popular—details.

For all of that, though, the Plus’ most notable contribution to Nike’s design history was something McDowell didn’t want to include initially. “They told me [the Tn Air logo] was a really big deal and I needed to feature it prominently,” recalls McDowell, who had devised his initial sketches without the now-iconic branding. Out of obligation, he threw a Tn Air logo on the heel and the sole which pointed towards the new Tuned Air technology. Today, that little hexagonal Tn Air logo is among the most famous in Nike’s design lexicon and has come to represent something beyond the sneaker that originally hosted it.

While revered for its visually distinct design features, the Air Max Plus also offered a host of technological innovations at the time, which made it a marvel of footwear design in the late ’90s. Most notably, the Plus was the first Nike shoe to feature Tuned Air. It was an important breakthrough for Nike, which had previously focused on making the Air unit as big as possible. Brute force was swapped out for a more delicate approach, where the goal was to distribute Air in a manner that provided efficiency and stability for the wearer. The Tuned Air unit featured what Nike called hemispheres—solid half-spheres inserted into the sole and Air unit—which allowed them to reduce pressure in the heel, while increasing cushioning at the forefoot.

On paper, the shoe—and the accompanying tech—looked amazing, but that would prove to be a problem. McDowell was informed that it would be impossible to make the type of faded upper he had envisioned. His retort was simple, if not naive: “we’ll just sublimate it.” Again, McDowell’s inexperience within Nike as a designer fed his ambitions; he was inspired by the Nike Flame running spike and felt it was possible to achieve the type of ombre effect he envisioned. He had the factory start with the lightest shade and print over it in increasingly dark tones. It took only one sample to get the desired outcome.

But, there was more bad news in store: The type of welding needed for the palm tree exoskeleton had never been done. Clearly not one to take no for an answer, McDowell suggested making the cage out of thin TPU, the same material Nike had previously used on small welded logos. The designer recalls being told to fly to Asia to test out the idea at the factory a mere two weeks before the shoe was due to be presented to Foot Locker. Upon arriving, he was told that the upper was too big for a one-piece weld, and that “it would take too much power and either melt the fabric or wouldn’t bond.” McDowell proposed making three separate welds rather than a single one. Much to everybody’s surprise —except perhaps McDowell— it worked and he returned to the United States with a pair of revolutionary shoes to pitch to Foot Locker.

The shoe was so impressive, and the Foot Locker representatives were so enthralled that, instead of commissioning a bevy of market studies, they made their way to a Foot Locker and put the sample on the shelves to see how young customers reacted. “Five or 10 minutes later, there were like 10 kids flocking to the shoe asking, ‘What is this? How do I get it?’’’ remembers McDowell. The staff at the store were equally puzzled, but the Foot Locker and Nike executives had seen all they needed to in order to green light the Air Max Plus’ production.

Despite the positive response, the Air Max Plus was facing a daunting task when it was released in 1998. The Air Max family had, by then, become a veritable behemoth, with the Air Max 95 and 97 helping to redefine the sneaker landscape. The Plus wasn’t slated to be the marquee Air Max shoe in 1998 and would have compete with a slew of other silhouettes from the family.

The original trio of Plus colorways would be instrumental in turning the shoe into what it is today. At the time, there was no such thing as a color specialist at Nike, so McDowell’s original Florida-inspired sketches were used to tell a three part story. There was the sunset —the blue and yellow, the night sky—the black with hints of red, and the sunrise—the blinding orange and yellow. For McDowell, this type of story-telling through multiple colorways was as much of a breakthrough as the introduction of Tuned Air, or the production of sublimated and welded uppers.

From the outset the Air Max Plus was the most expensive shoe at Foot Locker, checking in at $125. Luckily for the Plus, it coincided with the Air Max 98 boasting a higher price than previous Air-of-the-year offerings and may have been indicative of a more robust market, rather than the increased costs of the new tech. Then again, the 98 is largely thought to have suffered because of its price tag, while the Plus thrived. Perhaps, then, it tells us not about how robust the sneaker market was, but about how important it was to offer something new to customers.

For those looking to the Plus as a running shoe—which was its intended purpose—the price was indicative of the revolutionary nature of the tech it harnessed. Compared to alternatives like the 98, which boasted a similar price without any technological innovations, the Plus offered the best bang for one’s buck. On a cultural side, the steep price was a signifier of wealth. Despite being a Foot Locker exclusive until recently—it’s now stocked at select independent boutiques—the Air Max Plus gained a cult following in Europe and Australia. In those markets, the shoe is better known by two letters: Tn. The hexagonal logo, which McDowell was hesitant to include, came to define the shoe—despite its presence on other models. Ask about the Tn and you’ll be met with excitement and information; ask about the Plus and you might get some quizzical looks.

The Tn really took root on inner city streets, where it became a favorite among shady characters who had the means to afford a pair. Paired with the Plus’ unique and intimidating design, the Tn came to be the shoe of choice for those going for an “up-to-no-good” look. In France, the shoe is synonymous with racaille style —the equivalent of the British roadman— and is prominent in the Parisian suburbs and Marseille. In the U.K., the Plus is often held up as being emblematic of London’s youth culture and sneaker scene and was a fixture in raves and garage parties in the late-’90s and early-’00s. In Australia, wearing a pair of Tn often meant you were looking for trouble and the model became a fixture among criminals and in Australian prisons. Despite being adopted by the streets and despite being a Foot Locker exclusive, the Air Max Plus was also celebrated in fashion circles at the outset, with Vogue naming it one of the 10 most-wanted items in January 1999—alongside a mobile e-mail reader.

In North America, the Plus has enjoyed more muted success, though it still boasts a cult following among sneaker aficionados. Tn fans are unabashed in their love of the shoe and McDowell recounted seeing someone who had gotten the silhouette tattooed on their foot—including the sole. The Plus’ legacy is important for Nike. The brand itself considers Tuned Air to be most significant innovation in the history of Air until the 2006 release of the Air Max 360. Think about that for a second: For a brand that has made its reputation on innovation, Tuned Air stood out as the best technology in visible air (Nike’s choice sole technology) for almost a decade. Perhaps that’s why the brand provided annual updates to the Air Max Plus, making it a family of its own, until the 360 debuted. While none of the follow-ups can hold a candle to the Plus in terms of cultural or technological impact, some interesting models have come from the program—particularly the Air Max Plus 2, 3 and 5.

Despite fading from the spotlight in the mid-to-late-aughts, the Plus can still lay claim to two decades of uninterrupted sales and has recently become a focal point as retro trainers came to the fore. The Plus’ legacy has been evident over the last few years. The Tn Air branding was rejigged for the Nike Air Max 97 SK, which drew its colorway from the Air Tuned Max, a follow up to the Plus. Skepta, the London grime MC, wanted to pay homage to the ubiquity of the Tn in London, so the hexagonal logo was reconfigured in the shape of a British electrical outlet with “Sk” replacing the “Tn”. As the Air Max 97 took center stage for its 20 year anniversary in 2017, the Plus was used to pay homage to the 97 in a variety of ways—from Air Max Plus reworks in classic Air Max 97 colorways, to a fusion of the Air Max 97 upper on a Tuned Air sole. In another testament to the street cred the shoe carries in the U.K., customized pairs (or fakes) have popped up with a Burberry-lite pattern on the upper. Unfortunately, an official collaboration doesn’t appear to be in the cards, despite the British house’s examination of counterfeit Burberry for its recent collection. Meanwhile, across the English Channel, Nike unveiled official versions of the Tn to mark the derby between Paris St-Germain and Olympique Marseille, two markets where the shoe is well-entrenched.

2018 is a big year for the Air Max Plus. It marks 20 years of Tuned Air and Nike wants to translate the shoe’s cultish appeal into wider fandom. For a few years now, Nike has been offering hints at renewed focus being placed on the Tn. It started with the aquatic, shark-inspired Air Max Plus Ultra, which featured a streamlined upper and drew inspiration from the colloquial French name for the Plus. Then, there was a futuristic slip-on update that garnered a lot of attention, despite being a women’s exclusive. Those have been followed up on with a series of new shoes that touch on the TN, without being explicit rereleases. The most notable contribution to the Plus’ legacy has been the introduction of the Vapormax sole unit to the TN’s upper. The Vapormax Plus is what the Tn was in 1998: The epitome of Nike’s technological innovation and a performance shoe that is bound to become a lifestyle shoe. Both have featured the brand’s most advanced Air unit yet, and both were conceived for running, not the runway. More impressive, though, is that the Vapormax Plus looks set to do something no Air Max Plus sequel has done yet: Equal the success of the 1998 classic.

When looking back on it, the odds were stacked against the Air Max Plus becoming what it is today. It was a Foot Locker shoe, designed by a Nike rookie who couldn’t even draw the brand’s logo properly, but he challenged conventions because of he was naïve and refused to take no for an answer. It was exorbitantly expensive (for its time), but had the tech to stand out from the Air Max 98. That very price tag came to signify social status in certain circles. Ultimately, the Tn came to represent what made Nike, well… Nike. It was technologically advanced, but unapologetic in terms of design and uncompromising in terms of quality. If anything, it is the ultimate example of why the most celebrated Nike designers often emerge from curious backgrounds and relative obscurity: Sean McDowell didn’t know any better, so he made the shoe better.