Airlines hate 'skiplagging' and many will punish passengers who do it. Here is every US airlines' policy.

• "Skiplagging" has been around for ages, but the hack has recently gained popularity amidst soaring airfare.
• To "skiplag" means paying for a one-stop flight with the intention of getting off in the layover city.

Wondering what will happen if you actually try skiplagging?

The airlines don't really want to talk about it. When asked, most noted their contracts of carriage — the contracts you agree to when you buy a ticket — but declined to provide further comment to Insider.

But, if you take a look at their aforementioned rules of travel, you can get some clues as to what is and isn't allowed in terms of skiplagging, even though it can be a little complicated to wade through.

Basically, if you try to skiplag, you're violating the airline's rules — and they actually see it as a way of cheating the system.

While it makes sense that a flight from A to B via C would cost more because it's a longer distance, airline pricing is really more about what they think people are willing to pay.

A nonstop flight is typically going to solicit higher demand than one with a layover, and carriers know they can get a premium for it, making it more expensive than the less convenient one-stop.

Whether or not you agree with airlines' pricing practices, they have the right to punish passengers who skiplag.

Consequences include closing loyalty accounts, banning customers outright, canceling the return ticket for those that skiplag on the outbound flight, and even taking "legal action with respect to the passenger."

Some carriers have actually taken customers to court before, including Lufthansa in 2018. United Airlines even filed a lawsuit against flight booking website Skiplagged.com, a company that finds and sells hidden city tickets and continues to be a thorn in the side for carriers.

Fortunately, the courts many times side with the passenger in ski lag-related lawsuits.

Nevertheless, every US airline has something written into their COC that outlines the exact policies.

However, carriers like JetBlue Airways, Southwest Airlines, Sun Country Airlines, Breeze Airways, Allegiant Air, and Avelo Airlines are not as vulnerable to skiplagging because they only or near-only operate point-to-point networks.

There simply aren't as many opportunities to use the fare hack due to the minimal one-stop options.

Airlines with robust hub-and-spoke networks like Delta Air Lines, American Airlines, and United Airlines are more likely to see people take advantage of these throwaway fares. But, that also means the carriers have a higher risk of losing revenue.

In fact, American has become so strict that it recently demonstrated that it will cancel a skiplag ticket before the passenger even boards the plane if an agent thinks they are planning to skiplag.

With airlines becoming more aware of the cost-saving practice, passengers need to pay attention to the COC they agree to. Here's what each carrier has to say about skiplagging.

American Airlines

American has been particularly notable in its skiplag punishments, and its contract does explicitly prohibit the practice. These are the rules:

• Fares apply for travel only between the points for which they are published.
• Customers cannot use round-trip tickets for the purpose of one-way travel only.

It also outlines the consequences if the fare difference is not paid for, including invalidating the ticket(s), canceling any remaining portion of the passenger's itinerary, confiscating any unused flight coupons, and refusing to board the passenger and carry the passenger's baggage.

Alaska Airlines, Delta Air Lines, Frontier Airlines, Hawaiian Airlines, Southwest Airlines, and United Airlines

While there have not been as many public reports of skiplag punishments, these airlines also specifically call out skiplagging in their COCs. Frontier says the following practices are prohibited, with the other airlines saying the same in similar language:

• Back to Back Ticketing: The purchase or use of portions of tickets from two or more tickets issued as round-trip fares or other scheme for circumventing minimum stay requirements.
• Throwaway Ticketing: The purchase or use of round-trip tickets for one-way travel.
• Hidden City/Point Beyond Ticketing: The purchase or use of a ticket from a point before the passenger's actual origin or to a point beyond the passenger's actual destination.

Southwest describes the bookings as "fictitious," and says it has the right to — without notice to the customer — cancel hidden city reservations, not refund an otherwise refundable ticket, and even require customers to pay back any money Southwest fronted for things like bag delivery during travel.

Meanwhile, Hawaiian states that it will deny transportation to those it believes are skiplagging unless they pay the fare difference.

Alaska and United specifically say they can take legal action against the customer, as well as the usual consequences like revoking miles and elite status. United even threatens to permanently ban skiplaggers from flying the carrier again.

Allegiant Air

In a twist, Allegiant says it "does not prohibit or penalize what is commonly known as "back–to–back" or "hidden–city" ticketing," but it warns will cancel the return leg or any continuing portions if the first flight of a roundtrip or multi-segment itinerary is not flown.

Avelo Airlines, Breeze Airways, JetBlue Airways, Spirit Airlines, and Sun Country Airlines

These airlines do not explicitly use terms like "throwaway" or "hidden city" ticketing in their COCs. But, these airlines use this or similar language:

• Fares apply to transportation between airports via the intermediate cities, if any, specified in reference to that fare.
• Reservations may not be issued or accepted for transportation that will either originate or terminate at an airport other than the airport for which the fares are published.
• Purchasing a reservation without intent to travel is prohibited.

Breeze, however, told Insider it will not ban anyone who uses a throwaway ticket, though noted it does "not generally see that behavior as our pricing does not incentivize guests to skiplag."