(NewsNation) — There’s a growing trend of people booking so-called “hidden city” tickets to avoid flight delays and save money.

The practice within the travel industry is called “hidden city” fares, or “skiplagging.”

It works like this:

When trying to book a flight to a desired destination, travelers look to buy the cheapest airfare — even if that means booking a flight to a city that isn’t their final destination.

Say someone is trying to book a flight from Chicago to Charlotte on Friday night. Rather than pay $191 for a one-way direct flight to the Queen City, a ‘hidden city” ticket costs just $117.

How? The traveler still ends up in Charlotte, the difference is they’ve booked a flight from Chicago to New York instead with a connecting flight in Charlotte. Once arrived in Charlotte, the traveler just doesn’t board the connecting flight to New York.

However, while it could save you money on airfare, there are a couple of downsides to “skiplagging.”

For one, travelers can’t check a bag. If they check a bag, it will end up in that final destination (New York) rather than the one they are actually going to (Charlotte).

Also, they won’t receive frequent flyer miles for the second, empty leg of the flight.

Airlines hate this practice.

In fact, many airlines are cracking down on it. United Airlines even sued the creator of a hidden city travel website in 2015, claiming “skiplagging” was “deceptive behavior.” The judge dismissed the case, though, claiming the court didn’t have jurisdiction over the case, according to CNN Business.

In early 2021, American Airlines issued “skiplagging” warning to travel agents and travelers, threatening fees and potential bans from the airline, according to Simple Flying.

The airlines even issued an update on booking and ticketing practices, defining the practice and warning travelers of the repercussions. They even updated this memo by adding “Voluntary Changes” to their list as of June 16, 2022.

Simple Flying even reported that American Airlines billed a passenger $2,500 for an alleged 52 cases of “skiplagging.” And the airlines continues to monitor their systems for this practice.

Southwest Airlines is also among the airlines that are fighting back against “hidden city” tickets.