Posting up at the bar at Midwestern pasta restaurant Daisies in Chicago’s Logan Square in June, the bartender noted just one cocktail special: a Lost Plane, a rum-based variation of the Paper Plane. Daisies front of house manager Katherine Sturgill’s tart, sultry version comprised Kasama 7-year rum, St. Elder blood orange liqueur, Amaro Montenegro, lemon juice, and a few cinnamony dashes of Moroccan bitters.

A few paces down Milwaukee Avenue, Alex Barbatsis, head bartender at stalwart craft cocktail den The Whistler, was menuing the Last Plane Outta Midway, a Paper Plane-Last Word mashup of Rittenhouse rye, Campari, Maraschino liqueur, lemon juice, simple syrup, and Angostura bitters — “a touch more bitter and less sharp” than a Paper Plane, and with “a more favorable cost of goods,” he quips.

Meanwhile in Lower Manhattan, the namesake speakeasy Paper Planes is substituting floral Amaro Montenegro for herbaceous Amaro Nonino in its house Paper Plane cocktail. A cheekily named Avion de Papel uncannily resembles famed New York bartender Joaquín Simó’s Naked & Famous (mezcal, Aperol, yellow Chartreuse, and lime), with a splash of ancho verde. Bar folk descending on the city for Bar Convent Brooklyn last month may also have noticed that liquor brands of varying stripes and net worths — few of them associated with ingredients used in the O.G. drink — seemed hellbent on aligning themselves with the Paper Plane, making it their “hero” cocktail.

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“I would, though, be very happy if it knocked off the Espresso Martini from its silly, buzzy cocktail throne.”

Is the bright orange drink on track to achieve “Drink of Summer” status? Comprising equal, shaken parts of Amaro Nonino, Aperol, bourbon, and lemon juice, the Paper Plane was invented in Chicago some 16 years ago as a variation on the Last Word. This bittersweet, friendly yet beguiling whiskey cocktail quickly secured a place in the modern bartending canon for its unicorn build as a four-ingredient equal parter. It appears poised for an Espresso Martini kind of moment, though it bears nothing in common with this or fellow It Girl variation: the Martini. Is it the Paper Plane’s low-octane composition? Or perhaps that amaro is stepping tentatively closer to the mainstream? Maybe the Paper Plane has simply hypnotized the next generation of barkeeps.

Of course, with bartender darling status comes riffs on riffs — and the inevitable, age-old question: At what point does the Paper Plane (itself a riff, whew!) become an entirely different cocktail?

“From my vantage point, the Paper Plane has been very popular since Sam [Ross] made it for The Violet Hour in 2007,” says Abe Vucekovich, beverage director at Meadowlark Hospitality in Chicago. “I would, though, be very happy if it knocked off the Espresso Martini from its silly, buzzy cocktail throne.”

It makes sense that the Paper Plane is so ubiquitous in the city where it was born; indeed, the cocktail has been a top 25 best-selling cocktail at The Violet Hour every year since it debuted there, per head mixologist Toby Maloney.

Vucekovich, also a Violet Hour alum, recently added a Paper Plane riff at cured-meats-focused restaurant Lardon, also in Logan Square. Fly Like Paper contains equal parts Four Roses bourbon, lemon juice, Bordiga Aperitivo, and Amaro Montenegro, plus a few dashes of Angostura bitters for a “patio pounder” worthy of the M.I.A. song the drink homages. But he suspects other factors explain the drink’s recent ascendancy.

“A lot of times cocktails seem to start as a bartender’s favorite and then catch on with guests,” he says. “I think the no added sugar could be a reason, and the lower ABV could be another. But, at the end of the day, the Paper Plane is flavorful and refreshing and that has allowed it to, well, take off.”

An Equal-Parts Unicorn

Ross, the owner/operator and bartender of New York’s Attaboy (formerly Milk & Honey), Temple Bar, and recently opened Danger Danger, invented this four-ingredient cocktail for The Violet Hour after Maloney, a former Milk & Honey cohort, asked him to create a drink for the menu. Ross conceived the Paper Plane as a riff on the pre-Prohibition Last Word, initially combining Campari with lemon juice, bourbon, and Amaro Nonino. As Ross later told drinks writer and author Robert Simonson in an interview, after two days of mulling it over, he subbed in Aperol for Campari to get a more balanced result. He named the drink for M.I.A.’s downtempo, hip-hop chart topper “Paper Planes,” which anyone with a radio or near a bar in 2007 was probably hearing on repeat.

“There are older drinks that we have early recipes of that were and are still commonly considered to be equal parts — Negroni, Last Word, etc. However, these cocktails don’t work as equal-parts recipes; in equal proportions, they don’t bring about the fundamental balancing that the Paper Plane does.”

Like the song, the cocktail took flight quickly. Ross almost immediately added it to the menus at Little Branch and Milk & Honey in New York where he worked. Copycats and riffs ensued worldwide; the drink eventually inspired bars of the same name, including one in San Jose, Calif. For Simonson, who featured the Paper Plane in his recent cocktail book, “Modern Classic Cocktails,” the drink’s incorporation owes much to its accessibility: four readily available ingredients that can be shaken into a crowd-pleasing cocktail without the need for special syrups or infusions or, hell, even a garnish.

“If the drink requires equipment like centrifuges or has a three-day production process, you probably shouldn’t be surprised that it’s not the next big thing,” agrees George Lahlouh, co-owner of Paper Plane (the bar) in San Jose, Calif.

Yet the Paper Plane’s unusual makeup is what magnetizes most bartenders on first meeting.

“Equal parts drinks are super weird; like the good ones are a ‘rare as hens’ teeth’ sort of thing,” Maloney says. “Those things that really and truly work in equal parts, as a bartender, make you feel like you’re doing an up-close magic trick.”

Though they sometimes spring from laziness, equal-parts drinks shouldn’t occur arbitrarily in the virtuous bartender’s quest for balance between fat, acid, and booze in every cocktail, Vucekovich says. “There are older drinks that we have early recipes of that were and are still commonly considered to be equal parts — Negroni, Last Word, etc. However, these cocktails don’t work as equal-parts recipes; in equal proportions, they don’t bring about the fundamental balancing that the Paper Plane does.”

Why Now?

The notion of a whiskey cocktail for the non-whiskey drinker is a compelling one for the bartender and drinker alike — especially one offering something for everyone via citrusy, upfront sweetness, understated bitterness, rich body, and a tangy, rounded finish. Indeed, bourbon-loving, Kentucky native Sturgill initially fell in love with the Paper Plane as a refresher featuring a dark spirit, as did Lahlouh.

“There are others out there, like a classic Blood and Sand that uses Scotch, and modern classics like Phil Ward’s Final Ward cocktail [with rye whiskey, green Chartreuse, Maraschino liqueur, and lemon juice] — which is also great, by the way — but the Paper Plane just hits different,” Lahlouh says.

“No, it’s not alchemy, it’s gestalt. The whole is greater than the sum of its parts.”

Maloney wonders if the drink’s rise could be attributed to the fact that a new generation of bartenders with a much larger arsenal of ingredients at their disposal is discovering it. “I started in ‘92, and, like, we discovered Campari and Fernet Branca and that sort of thing,” he says, “but bartenders now are awash in amaros and indoctrinated into that world early in their careers. And this is just such an elegant usage of Nonino.”

A niche ingredient as recently as 10 years ago, Amaro Nonino, with its quinine bittersweetness and caramel sweetness, now finds itself in a crowded field of amari that range from bright and citrusy to bracing and minty. Maloney, for one, wouldn’t necessarily drink Amaro Nonino on its own, though he thinks that’s partly why it works so well in this cocktail. “It’s alchemy,” he says. “No, it’s not alchemy, it’s gestalt. The whole is greater than the sum of its parts.”

A Riff Too Far?

Unpacking the carefully calibrated Paper Plane helps one understand that cocktails are designed with specific ingredients because that’s what they taste best with. Yet it’s in a bartender’s creative nature to sample, repackage, push, and improve, even when dealing with “the Highlander of cocktails,” Maloney says.

Indeed, more than most, equal parters seem to dangle an open invitation to test the limits — “subbing out a spirit for a comparable alternative or going off the wall and totally mixing it up just to see what happens,” Lahlou adds. “I think about the Last Word cocktail especially and the crazy amount of iterations that drink has — the Naked & Famous, Final Ward, La Ultima Palabra, etc., etc. Ultimately, curiosity leads us to the next new thing, and lucky for us, there’s a lot of curious bartenders out there.”

Ward famously described this as the “Mr Potato Head approach” — a.k.a. just take him apart and dress him up differently — which inspired many of Ward’s now-famous creations. Indeed the uninitiated customer tasting a Paper Plane riff might sense something familiar in its repackaged, drinkable bass line, but never quite get to the bottom of it unless the bartender brings it up.

Is that a bad thing?

It’s not unlike the throngs of listeners who’ve loved M.I.A. ‘s 2007 hit without ever learning that she sampled the Bossa Nova-esque, 1982 Clash song “Straight to Hell,” which dealt with similar themes of xenophobia and immigration.

Then again, sampling theoretically requires permission from the owners of the composition and recording before said sampler releases copies of their new song. The same can’t be said for the riffs-on-riffs bar industry, which lacks a reasonable framework for intellectual property rights.

It often comes down to establishments and bartenders crediting drinks’ creators, all the more important when “the drink is not that old and the bartenders who made them are still out there walking among us,” Lahlou says. That’s partly why, rather than riff on the riff, he’d rather play the O.G. on repeat in all its unicorn glory.