Im sure there are threads on this, but I couldnt find them.
Has anyone actually run into problems by not using the second half of a booked r/t ticket?

Im looking to do this on a lgw/ams flight on KLM (booked on delta.com)

Theres quite a few discussions about this on various airline forums on FT.. It has been done.. but some phone calls from the airline legal department might start appearing on your phone machine if its done too often. Often airlines gives discounts on certain routes, and must be completed.. the other factor is if you do this on departure and not get on your last segment, they may cancel the remainder of the ticket. Missing the last leg on arrival is probably the safest.. but again, airlines may start keeping records of skipping out, and may pursue legal action to get the fare difference from you back. These are only a few of the many things that can happen talked about here on FT.

I believe there are even threads about this on the first page. It's called throw away ticketing and is against the contract you make with the Airline when you purchase the ticket. Failing to fly both segments gives them the right to reprice the ticket as a one-way and charge you the difference.

You are free to do it whenever you wish to. Airlines do not audit ticket coupon usage except upon a complaint by a passenger.

The reason you can do this at any time is largely because the airline retains rights to do things like change seat assignments, cancel flights, re-route passengers, etc. As a passenger, you also retain the right to make changes and the carrier has no penalty adjudication ability any more than you can bill the carrier a $25 seat change penalty.

Their is no legal concept or theory, as a result, that the carrier can utilize against you. That is why they do not and will not enforce it.

For instance, I was in White Plains on 9/11 when commercial aviation shut down for 4 days. I rented a car to get back to Dallas and threw away my return AA ticket. I dropped one person in Memphis and 2 people in Little Rock on the way.

What you do when you get to where you're going is not within the control of the carrier no matter what anyone at Delta tells you.

Still the same brash attitude and bad advice... you've actually motivated me to find the "ignore" feature I keep hearing about.

It may be brash, but it is the truth. Nobody can force you to complete a trip, no matter what the airlines says. In my 45+ years of flying, I have l used over a hundred throw-away tickets to many places in that time. I have not received one phone call, letter, email, inquiry or second look.

Let me summarize for you:

1) The airline will (most likely) cancel your itinerary as soon as you skip one of your segments. So don't try it unless you're on your way home.

2) It's against the airline's rules.

3) The airline probably won't do anything to you, particularly if you only do it once or twice.

4) A group of FlyerTalk readers will organize a mob and try to hunt you down. A second group of FlyerTalk readers will come to your defense and a great battle will ensue. (Think "Braveheart" but with Roll-aboards instead of horses, laptops instead of swords, and "Diamond Medallion" hats instead of helmets )

To the OP - Once you miss one segment, the balance of the trip will typically be cancelled. Make sure you don't stuff this part of it up.

Can you point to one specific instance where you have first or second hand knowledge of this actually happening ?

I've seen lots of theoretical discussions, but never one poster who's had an airliner go after them. I don't think their software is that dependable to go after someone when they might be wrong. After all, how often have they failed to credit your miles?

This is much better advice... it is against the rules, and the airline could probably come after you based on the CoC (though there are very few occurrences of this happening and it's usually the biggest fish). The biggest thing is to be aware of the itinerary cancellation, so be sure not to foul that up.

Perfect!

If you don't complete a segment, the rest of your itenerary is automatically canceled (you have to call them to rebook; pay fees, etc.). If you only throw away the return trip & don't rebook, while it IS against the airline rules, realistically, people miss flights every day on every flight due to changing circumstances (esp business passengers, the airlines' bread and butter) and don't rebook. Airlines do not bill you for missed flights. This is why airlines routinely over-sell flights.

So many straight and honest people in this forum gives me hope that the world has a chance.

Funniest thing I have ever read on Flyertalk!

KLM has no prohibition (some reservation agents even encourage it) so feel free to not use the return. It would be good to let them know after your first leg that you won't be using the return.