What is skiplagging? All about the travel hack airlines hate.

It’s called skiplagging, and although it sounds playful enough, it’s hardly a game in airlines’ minds. In fact, most carriers regard it as a form of fraud.

Here’s everything you need to know about the controversial practice.

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What is skiplagging?

“Skiplagging — or ‘hidden-city ticketing’ — is booking a trip where you plan on getting off at a layover city and throwing away the last leg or legs of a flight,” explains Clint Henderson, an industry expert and a managing editor for the Points Guy.

“Say I want to fly to Miami from New York,” he says. “Prices are high if I book direct, but if I fly New York to Miami to Orlando, I can save $130. I could book that, pocket the savings, and then get off the plane in Miami instead of continuing on to Orlando.”

It might seem counterintuitive: You’re ultimately flying fewer miles in the sky, so why should it cost more money on the ground? Well, airlines typically price flights with a connection at a lower rate than directs because the latter are often in higher demand. Plus, as Henderson points out, carriers want to route as many passengers as possible through their dedicated hubs to increase efficiency and thereby cut costs. That means you can usually save money by connecting through one of these primary bases of operation.

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In the case of the teen in Gainesville, he was booked on a flight to New York City by way of Charlotte — a major hub for American Airlines. His family is based in North Carolina, however, so he never had plans to get on the connecting flight to New York, his father, Hunter Parsons, told local media. Gate agents became suspicious of his intent after seeing his North Carolina license. That’s when he was pulled aside for questioning, his ticket was canceled and the family had to purchase a new one, Parsons said.

Multiple news outlets have reported that the teen was “detained” during the incident, but a spokesperson for American Airlines refutes that description.

“Our records indicate the customer was questioned only at the ticket counter about their travel, while attempting to check-in for their flight,” AA spokeswoman Andrea Koos said in an email. “A member of our customer relations team has been in touch with them to address their concerns.”

What are airline policies on skiplagging?

The fact that the teen was denied boarding underscores how serious airlines take skiplagging. It makes sense, because the practice saps revenue from them on two fronts: Not only do passengers underpay — potentially by hundreds of dollars per ticket — but the seat on the tossed leg also could have been sold to someone else.

Most contracts of carriage from major airlines expressly forbid skiplagging as a result. If an airline catches you trying to do so, it could cancel your whole itinerary. Henderson also points to examples of travelers having frequent-flier miles and memberships rescinded, or even rare instances of passengers getting sued.

“The airlines are getting increasingly sophisticated and smart about it,” he adds. “I expect that will get even more prevalent as technology improves further.”

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In the meantime, it remains a somewhat sticky subject in travel. It can be difficult to prove what a passenger’s itinerant intentions truly are.

Matt Meltzer, a Miami-based travel writer, said he has saved hundreds of dollars on flights by skiplagging over the past several years. He views the teen’s recent experience as an outlier and doesn’t think gate agents at major hubs are looking for skiplagging.

“If I was getting on that flight and someone accused me of not intending to fly to New York, I’d just say: ‘Nope! Got “Hamilton” tickets tomorrow night. Very excited. Go Mets!’”

And it’s not exactly a solid business practice to preemptively accuse your paying customers of fraud. Representatives from both Delta and United declined to comment for this story; Delta pointed to a link to the airline’s Contract of Carriage, which expressly prohibits hidden-city ticketing. United, American and Southwest also prohibit the practice in their contracts.

So should you skip skiplagging?

Despite airlines banning the practice, some travelers are shirking the rules — and there are resources dedicated to helping them do it. Most notable is Skiplagged.com, which helped popularize the practice, and the term itself, when the site launched in 2013. (United Airlines and Orbitz unsuccessfully tried to sue the site a year later.)

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Be forewarned: On top of earning the ire of airlines, skiplagging comes with its own spate of logistical headaches. Chris Dong, a Los Angeles-based travel writer and points expert who used to skiplag, says you especially can’t do this on a round-trip flight.

“Airlines will cancel your return flight if you’re a ‘no show’ for any segment of a booked itinerary,” Dong said in an email.

If there’s a schedule change, or if a flight is delayed or rerouted, which can be common in a stormy, busy travel season, then, as Dong points out, “there’s a possibility your entire skiplag plan could go out the window.”

Finally, Henderson introduces another pitfall: “What if you are last to board, and they make you check your carry-on?”

“You’ll be in trouble, because your bag will end up in the wrong city,” he said. “The airlines can take your loyalty account, ban you from the airline and even sue you. It’s definitely not worth the risk to try this just to save a few dollars. Don’t do it!”

Brad Japhe is a London-based travel writer. You can follow him on Instagram: @journeys_with_japhe.