Reader geoff asks,

I am looking into $$$ flights from Las Vegas – Toronto. I am finding that non-stop flights are pricey. It is much cheaper to book one way from Las Vegas to Winnipeg connecting in Toronto and just miss the connection. Is there a compelling reason not to do this? TIA

It’s against airline rules (although the New York Times “Ethicist” column says it’s perfectly fine).

If you put the frequent flyer number of the airline you’re flying in the reservation they could do something unpleasant to your frequent flyer account.

They probably won’t, at least unless you do this very regularly. But I like to use a partner frequent flyer account in the reservation, just in case, when doing any kind of throwaway ticketing.

Travel agents who did this regularly for clients would get ‘debit memos’ — requiring them to pay the difference in fare (or risk losing their ability to issue tickets on the airline). Individual flyers aren’t forced to pay up.

This technique is most useful when you are flying to an airline’s hub city since they’ll have connecting flights beyond the hub. Just pick a (usually nearby) city to fly to where fares are cheaper, likely because of competition from low cost carriers or because there’s less business travel. Just avoiding non-stop markets dominated by a hub carrier can be sufficient due to greater competition.

As a general matter,

• As long as you’re only skipping the final segment of the ticket you’re not going to cause problems for your return. You don’t want to do this on anything other than the last segment in your itinerary (unless you really know what you’re doing, you can sometimes skip a flight on one airline when the rest of your itinerary is on another).

• So you want to do this with one way tickets, or with the final segment of a roundtrip only.

• Normally you can’t do this if you’re checking luggage because your luggage will wind up at your ticketed destination, not where you’re ending your journey. With many international flights you’ll have to claim your luggage anyway and you can just not drop them back off.

Let’s say you wanted a one-way New York – DC flight.

You could ticket New York – DC – Jacksonville for less.

There’s always the risk of irregular operations — that your flight will get delayed or cancelled and the airline will want to reroute you through a different city. I’ve never actually had a problem insisting on my original routing (and I’ve even concocted some squirrely reasons why I needed this, like “I’m having an affair in connecting city ____, don’t worry I only need 45 minutes…”). But it’s something to deal with.

You’ll want to check out my guide Using Hidden City and Throwaway Ticketing to Save Big Money on Airfare and see how this technique can sometimes save on fuel surcharges on your award tickets as well.