I am looking at some flights that go to Europe on AA/BA. The route is SFO-LHR-CPH. I don't have much interest in going to CPH and I am trying to go to LHR for most of the trip, then continue on to CPH for a couple days, then fly home.

The fare rules say no stopovers though, so I want to double check that this means I cannot do what I planned, as I can't change my LHR to CPH flight for a week later, and need to make my connection in LHR as it is booked?

It does however say transfers are permitted. I am not sure what this means? Does anyone have any advice or tips, so I can do my LHR trip?

Here is what it says:

Category 8: Stopover restrictions

NO STOPOVERS PERMITTED.

Category 9: Transfer restrictions

2 TRANSFERS PERMITTED IN EACH DIRECTION FREE
2 FREE IN EUROPE IN EACH DIRECTION.
AND - 2 TRANSFERS PERMITTED IN EACH DIRECTION FREE
1 FREE BETWEEN AA/AY/BA/IB/US AND AS IN LAX/PDX/
SEA IN EACH DIRECTION
1 FREE BETWEEN AA/BA/IB/US AND AM IN MEXICO IN
EACH DIRECTION
1 FREE BETWEEN BA AND AC IN CANADA IN EACH
DIRECTION
1 FREE BETWEEN AA/BA/US AND WS IN CANADA IN EACH
DIRECTION
1 FREE BETWEEN AA/AY/BA/IB/US AND HA IN HAWAII
IN EACH DIRECTION
2 FREE BETWEEN AA/AY/BA/IB/US AND AA/AY/BA/IB IN
NORTH AMERICA IN EACH DIRECTION
FARE BREAK SURFACE SECTORS NOT PERMITTED AND
EMBEDDED SURFACE SECTORS PERMITTED ON THE FARE
COMPONENT.

Typically transfers are <24 hr in duration. So, no, you likely cannot change your ticket to have 5 days in LHR.

This is like the distant cousin of the hidden city prevention mechanism.

That's too bad. Is there any tips to get around this? Or am I stuck only having a less than 24 hr stop in LHR, and have to continue on to CPH?

You can always just book a flight to LHR...

Pay $$$$ to change your ticket. This can be a small amount or a large amount. You will not know until you ask. Staying longer than 24 hours will invoke the UK APD

Your options:

1. Pay to make the change (or buy) your desired routing, it's not clear from the post whether you've purchased yet or not. Or...

2. If your return flight home is on a different PNR and ticket, just skip the LHR-CPH leg and buy a separate ticket for that. But this will cancel any remaining legs on the SFO-LHR ticket, so don't do this if it's all one ticket. Or...

3. Buy a separate CPH-LHR-CPH roundtrip. Fly the SFO-LHR-CPH flights, then backtrack to LHR on the new ticket.

4. Spend time in CPH instead of LHR.

Do you actually want to be in CPH at all or did this just pop up as a cheaper (hidden city) ticket?

Transfers or connections under 24:00 are permitted; stopovers of 24:00 or longer are specifically excluded.

To change that, you would have to reprise, probably pay fare and change fees and have the trip re ticketed to a fare bucket that includes the stopover (possibly two tickets?)

As mentioned previously, a stopover of 24:00 or longer will further invoke the U.K. Air Passenger Duty.

Thanks everyone. I haven't bought yet, it was just a very cheap ticket to CPH. I will probably pass, as changing things, or adding on another separate route will just add money and make the ticket almost as expensive as it normally would be.

Rather than giving up based on "probably" why not:

1. Price the ticket you really want. You may be surprised.

2. Buy a SFO-LHR roundtrip and then buy a roundtrip to CPH on either BA or a LCC. Again, you may be surprised.

Do understand that your departure from LHR will now include the APD which does add to the taxes.