Last week I wrote about an American Airlines passenger flagged for throwaway ticketing or ‘skiplagging’ to save money on their flights.

They checked in at the ticket counter and showed their ID. The agent saw that it was an ID issued in the state they were connecting in – suggesting they might be stopping their journey there. The agent said they suspected the passenger planned to skip the final flight segment and warned them they would be banned from American Airlines if they did not take the connection.

Busted. The passenger had planned to skip that last flight. They ultimately did skip it. We don’t know if American Airlines has banned them or not. However there is already another one and this story is even more striking.

Last week I booked a last minute flight that had a layover in the city I live. Since I knew I was skiplagging, I didn’t use my frequent flyer number to avoid linking it to my AA account. When I went to check in, the system asked me to check with the counter.

I initially thought it was because it was a full flight or something along those lines, but when I spoke to the agent, she told me that the system had flagged my reservation because my address (from my profile) was near the layover city. She said if I didn’t board the second leg of the flight, I’d be put on the DNF list.

In the end, I ended up boarding the second leg and buying a separate flight that departed an hour after I arrived for less than $60 to get home. …[I]t made me wonder if changing my address in the profile to a different state would let me do this again without getting flagged?

They knew what they were doing. They took precautions. They didn’t want to risk their American AAdvantage account, so they did not add it to the reservation. But American Airlines still figured out who they were, where they lived, and knew they were connecting in their home city.

American Airlines has been known to be quite aggressive clamping down on ticketing techniques that save customers money.

• There was the teenager taken to a security room and interrogated over their throwaway ticket (they confessed).
  
• They’ve also been confronting passengers at the airport over suspected ‘ticketing abuse’ and billing them although there the ban only applies if the customer doesn’t pay.

Here we’re seeing a couple of similar incidents – tracking where a customer lives and comparing it to their connecting city – and having the airline block online or kiosk check-in so that an agent can deliver a warning.

Throwaway ticketing is not illegal but it breaks the airline’s rules. Airlines often charge more money for non-stops than they do for connecting itineraries. So people book a flight with a connection through the city they want to travel to, and just don’t take that second connecting flight. That saves money, and the airline sees it as costing them money.

For instance, you:

• Want to fly New York to Denver, but it’s cheaper to book New York to Denver to Colorado Springs – so you buy that, and only use the first segment to Denver.
  
• Want to fly DC to Phoenix, but it’s cheaper to fly DC to Phoenix to Tucson – so you buy that, and only use the first segment to Phoenix.

If you do this, and an airline catches you, they might ban you or shut down your frequent flyer account. Historically there has been little risk to this if you do not do this frequently. However, plenty of things can go wrong along the way.

• Re-routing during irregular operations. If your flight is delayed or cancelled, your airline may want to re-route you through a different hub than the city you actually wanted to fly to (and get off in).

  Maybe your connection would go through Chicago instead of Denver – and you wouldn’t be able to get off in the city you’d planned to! I’ve never had a problem asking to be kept on my original routing during irregular operations, but it may not be automatic.

• No checked bags. Airlines don’t generally allow you to ‘short-check’ bags, where they only send your luggage to your connecting city, although there are exceptions. If you book DC to Chicago to Milwaukee, and you get off in Chicago, you don’t want your luggage sent to Milwaukee (yes, your bags can fly without you).

• Gate checking bags. If you aren’t among the first to board your flight, overhead bins may be full (or employees might fear that the bins are filling up) and you might be required to gate check your carry-on bag instead of bringing it onto the aircraft. Then your carry-on will go to your final ticketed destination, not the city you’re flying to.

• Can only book one-way. If you book a roundtrip, and throw away a segment on your outbound, the rest of your itinerary will get cancelled by the airline. You might need to book that DC – Chicago – Milwaukee as a one-way ticket if you’re getting off in Chicago, and then a one-way back to DC on the return (potentially with a throwaway segment on that ticket, too).

Computers are much more effective than they used to be at noticing patterns and checking large amounts of data – like passenger reservations – for out of sample behavior. That suggests airlines are only going to get better and better at identifying cases where their rules are being broken. They’re going to have a lot more resources thrown at AI than customers will have defending against those. And government ID requirements make it harder to keep airlines from knowing everything about you when you travel.