I want to fly from San Francisco to Amsterdam on Northwest and have noticed that, for some reason, it costs more to fly from SF to Amsterdam than it would to fly from SF to Amsterdam, change planes and then fly on to London.

Has anybody ever booked the cheaper flight (SF-AMS-LON) and simply left the airport in AMS rather than continue to LON? I would not plan to check baggage.

If I did this, would I be able to board the return flight in AMS if I did not start the flight in London?

I don't think you can do that.

If you did that your return ticket would most likely be voided and you'd have to pay for a full fare walk-up ticket to get back home.

Yes, you can do it as long as you hold individual tickets for each leg of your trip and don't check any bags. Your return ticket will NOT be invalidated, just re-confirm your return flight from AMS a few days before departure.

Brotherleelove: The OP is not talking about individual tix - the question is about a flight from SFO > London via Amsterdam. It would be one booking and the return ticket would most likely be voided.

Now IF they were two different bookings -- RT SF/Amsterdam and RT Amsterdam/London - that is a whole different issue. But that is not what Stanyan describes.

The reason it's cheaper to go to London via AMS, rather than stopping in AMS is got nothing to do with number of legs or distance. It's purely competition. Northwest has lots of competition flying into London, but very little into Amsterdam. So, they can charge more for easy non-stops into Amsterdam, but have to cut prices to get the London business. We have a NW non-stop to Amsterdam from here in Memphis too. More expensive than the AMS connection to Frankfurt.

As others have said, if you buy the round trip on NW/KLM, then don't take one of the legs, all of the following segments get cancelled, including your return home, and you're stuck. They thought of that idea themselves, long ago.

Hi S,

What you are contemplating is a "hidden city" itinerary.

It is a no no.

>If I did this, would I be able to board the return flight in AMS ...

No.