Most travelers know that causing unruly behavior on a flight can lead to dire consequences, but many may not realize that you can also get in big trouble for not setting foot on a flight at all. While missing a leg of a flight might sometimes be unavoidable due to changes in travel plans, savvy travelers have been purposely missing the second leg of their flights for years to save hundreds of dollars on fares. Recently, Lufthansa Airlines even sued a passenger €2,112 ($2,374) for this practice, which is known as “hidden-city ticketing.” (A Berlin court dismissed the suit, but the carrier plans to appeal, according to CNN.)

But are the fares legal, and is it worth checking them out? Here’s what you need to know.

What is hidden-city ticketing?

The “hidden cities” in this context are all of the places that become much cheaper to fly to when you’re supposed to only be there for a few hours on a layover instead of a final destination. To be clear, we’re not talking about mystical destinations such as Colombia’s Lost City (although you should still definitely go there) but places such as Detroit or Houston that become much cheaper to fly to when they’re the appetizer instead of the main meal of your three-course flying experience. That’s because airline pricing depends on a lot of factors besides just the cost of fuel—competition on the route, the popularity of business travel, and other factors play a role.

As a hypothetical example, let’s say we’re flying from Boston to Oklahoma City and looking for flights. If you scour the main search engine websites such as Kayak or Google Flights, you’ll see many connecting flights to Oklahoma City with stops in other places such as Philadelphia or Chicago. However, the goal in hidden-city ticketing would be to find a journey where Oklahoma City is the layover on a flight to a final destination you don’t plan to visit. In the end, that could look like buying a flight between Boston to Los Angeles and getting off the plane with no intentions of setting foot on the West Coast.

So, how does one reveal these so-called hidden cities? The website Skiplagged pioneered this practice and is still up and running, even after United Airlines and Orbitz sued the company’s founder Aktarer Zaman in 2014 (Orbitz settled and the remaining case was eventually dropped because the judge said that court didn’t have jurisdiction, CNN reported). Today, Skipplagged has a “few million” active users per month that scour the website for flights or hotel deals, says Skiplagged’s Head of Design and Experience Philippe Ramet. These could be for hidden-city tickets that make up “a bit more than 20 percent” of flights on the website, or for the more “regular” flights that go from point A to B per usual.

While it’s true that you can save a lot of money using hidden-city tickets, we suggest looking at other options first due to issues that could arise at the airport and after the trip.

Is it legal?

Hidden-city ticketing tends to go against airlines’ rules, but actually getting sued for the practice is unlikely for those not doing it often. Lufthansa says “legal disputes in this context are very rare,” in part because recalculating the fare the passenger would have owed must follow certain laws.

Skiplagged says on its website that these hidden-city flights are “perfectly legal.” It looks like this is now the case for those traveling on Iberia due to a recent Spanish court decision. But regardless of the possible legal interpretations of hidden-city ticketing around the globe, there are still consequences and considerations that could affect your trip and relationship with airlines.

What are some possible trip complications?

One of the biggest reasons why it might be a good idea to look elsewhere for travel deals is that traveling on hidden-city tickets requires you to remember a lot of little rules.

For starters, flying on a hidden-city itinerary requires being extra careful about your baggage. Skiplagged tells customers not to check bags, but notes that even carry-ons could pose an issue if there’s not enough space on the aircraft. While some airlines can gate-check bags, others might check it to the final destination if there’s not enough room.

Another downside of traveling with hidden-city tickets is the risk of weather-related or logistical issues throwing a wrench in your plans. For example, you could be on a flight between New York’s John F. Kennedy International Airport and Los Angeles with a stop in Chicago, but the airline would prioritize getting you to Los Angeles before putting you on another itinerary that happens to stop in Chicago. Offering to go to Chicago anyway through another itinerary could raise suspicion that you are purposely intending to get around that carrier’s fare rules.

“Hidden-city is a risky move to make; it is not without some potential risks to the traveler,” says Henry Harteveldt, travel industry analyst and president of San Francisco-based Atmosphere Research Group. He notes that if the itinerary changes, “the airline has every right to rebook you on one of those different flights.”

Airlines could cancel the rest of your flight if you don’t show up for one of the legs, so hidden-city ticketing is also unreliable for round-trip fares. There may even be an added cost in some cases.

“If a customer does not show up for his outbound flight, the return flight is still available to him as originally booked,” a Lufthansa spokeswoman told Condé Nast Traveler when asked if passengers get any warning before the airline takes action against hidden-city ticketing. “However, Lufthansa will then recalculate the ticket price which corresponds to the actual travel route (e.g. one-way fare).” Anyone who foresees missing a leg of a flight should notify the carrier immediately, she said.

And these are just the issues in transit. There are also some bigger consequences you will have to think about if you plan to use hidden-city ticketing.

What are some of the bigger consequences?

There’s a good chance you might not run into any of the above-mentioned problems, but you’ll also have to be aware of the potential, bigger consequences of using hidden-city ticketing.

A passenger that skips a leg of a flight for any reason once probably won’t get in trouble, but if the pattern persists there could be issues. Skiplagged warns customers on its website not to “overuse” these itineraries: “Do not fly hidden-city on the same route with the same airline dozens of times within a short time frame,” it states.

But how much is too much? Harteveldt warns that airlines now have better technology to catch those abusing the practice, and that flying hidden-city flights even once a year for several years might be enough to draw a carrier’s attention. He notes that eventual consequences could include sternly-worded letters asking for payment (like the one an elite reader of The Points Guy reportedly received), lawsuits, a forfeiture of frequent-flier miles, or even getting banned from an airline.

“Don’t say it can’t happen to you, because it could, and it doesn’t matter what route, what cabin class of service, what your frequent-flier status is or anything else,” Harteveldt says. “If you are serially abusing hidden-city fares, the airlines will at some point catch you—and they will take action.”

Where can I find my airline’s rules?

Whether using hidden-city flights or not, passengers do enter into an agreement with airlines about how their tickets can be used. These are outlined in a document known as the “contract of carriage” or “conditions of carriage,” and can usually be found on the airline’s website.

Chances are you’ll be going against an airline’s rules if you buy a ticket with the intent of missing a flight. American Airlines’ conditions of carriage, for example, note that “reservations made to exploit or circumvent fare and ticket rules are strictly prohibited.” It cites hidden-city fares as an example, along with some other activities including buying a ticket just to use the lounge or booking a ticket for someone without their permission. American says if you are exploiting the airline, it could “charge you for what the ticket would have cost if you hadn’t booked it fraudulently,” cancel the rest of the itinerary, or even refuse that person the right to fly.

How else can I save money on tickets, legally?

Airline pricing isn’t straightforward, but knowing some tricks of the trade can help you find airfare deals without setting yourself up for the pitfalls of hidden-city ticketing. For example, routes with a lot of competition and low-cost carriers can lead to better deals, Harteveldt says.

Using a price tracker such as those available on Kayak, flexing your loyalty accounts or checking out one of the many e-mail lists for deals are all good options (Condé Nast Traveler has compiled several tips here). So, regardless of whether you’ll get caught, we suggest searching for other alternatives and paying a little more for some peace of mind.