Is there any problem doing this?

I was planning to use reward miles for my return flight and therefore, only pay for outward flight.

Ł700 for one way flight london to new york, or Ł350 return? Doesnt make sense

Technically they can come back and charge you for the difference between what you flew (one way) and what you bought (round trip) when you fail to use the second half of your round trip ticket.

But if it happens just once you might be lucky and get away with it.

most people would buy the return ticket....

do you need to spend the mi for some reason?

it isn't unusual for return [round trip] tickets to be cheaper than 1 way.....been that way for the 50 years i've been flying....

Well being from UK dont get to use Continental that often. And I heard they're going to expire if you dont use them once every 12 months now? (Is this right?)

if your ticket is on ua, co, or usair, you can credit the flights toco/ua which will count as activity & extend the expiration...

We've been back from our European Adventure in September for a month and all of our inter-European flights were booked as return (because of the ridiculous cost of one way fares) and we didn't use any of the return tickets and there was no repercussions from the airlines. If airlines want to cost one way fares at over twice the price of a return fare then people like me are going to continue to book return and just forget about the return leg.

look at the co site and see what you can do w/ mi's....we have donated mi and bought subscriptions to extend expiration dates....but don't know what is available to you in the uk....

No idea what the Contract of Carriage was for your tix inta-European, but as others note in this thread and all over FT, don't do it on a repeat basis in the USA. Pretty sophisticated software to "sniff" our fraud and the carriers take it seriously.

In addition to refaring each ticket, they will also zero out your FF account if you used one and that gets ugly.

I have no idea what the Contract of Carriage was as the flights were booked here in Australia by our very competent and experienced TA. Our last of 9 trips to the USA was in 2004 and as we have no intention of ever going back whilst the current level of paranoia exists in U.S airport security being "sniffed out" does not concern us - paying the best price for a ticket does.

Yeh. But what I mean is after this its possible I wont use CO or UA for some time so the miles could well expire.

To be honest, its about 1 trip a year to North America for me.....

Good to know.... :-)

Good point. I guess ANY account activity would stop the points expiring?

Yes, we can access account same as everyone else, so I could move points around etc I guess to keep account active. Didnt think of that.

Can you donate to charity? If so, whats minimum miles to donate? It would be worth it if I could donate 1000 miles just to keep account active.

I appreciate that if you systematically do this they're not going to be happy. But surely they wouldnt pursue you for a one-off?

Also, what can they do? Surely they cant legitimately charge your credit card for the full single fare?

Wrong. If your question is whether "they" (the carrier) could charge you for the one-way, you haven't read the t&c as well as the terms of the debit issued for your original ticket (paper or online charge).

A carrier which found this to have ocurred would simply refare the ticket and issue a debit for the correct fare difference. If you read through, you will see that you are obligated to pay the difference. You would have the option, here in the USA, and in most countries of initiating a chargeback, but would lose. This is no different than a hotel's recourse if it turns out that you swiped the towels and you've already checked out.

If the question is whether this is likely to happen if you do it once, the answer is that it's very unlikely.

The more likely result in general, and sometimes the greater hook is that the carrier simply zeroes out and closes the FF account. For people who bank 500K+ miles, that is a devastating hit.

Shows the anti-fraud system is working here in the US. The goal is to keep people out who abuse the system over here. If another country and its businesses want to let it go, that's all about why different systems function differently.