Is this one single ticket/PNR or two? That makes a big difference in whether you can check bags through and how much time to allow.

Two different tickets. one BA CPH to LHR and another ticket LHR to LAX. I assume then we collect bags. So possible arriving 12:10 and having to depart 3:05 (so board at 2:05 most probably) isn't enough time. we can take the earllier CPH to LHR flight. no sweat.

This is all VERY helpful.

If things work well, three hours is more than enough time. However if your first flight is late or luggage is delayed and you miss the check in deadline for the second flight, chances are (depending on the fare rules) that the entire value of your TATL ticket will be lost. So it's a big risk than can be minimized by taking an earlier flight. Some people would suggest arriving into LHR the previous evening to allow a wider margin for error. This could be more pleasant than a very early morning flight and then a long layover before a long flight.

Ah, yes. Makes sense. Gonna be either the 7am flight or evening before. If we do early morning we get another full day in CPH. Hmmm... we'll figure that one out but the flights info from you and everyone else has been a big help. Thank you.

Separate tickets then BA will NOT interline. They won’t even do it for BA~BA separate tickets. You will have to clear UK immigration and customs in T5 and then take the bags to T3

Also depending on the BA ticket type you may very well have pay a change fee - even if flying Club Europe.

3 hours is possible
 

I just did this at LHR last month. Diffternt end point but the 3 to 5 xfer isn't bad with the purple busses. Esp if you have any status for expedited immigration into UK and security back into LHR.

To be absolutely clear, OP CANNOT use the purple transfer buses.

Because OP is on separate tickets with checked luggage OP will need to:

- go through passport control at T5 (could be long wait for non-EU passport)
- wait for bags and exit T5 through customs
- take the Tube or Heathrow Express to T3
- recheck the bags at AA check-in at T3
- go through hand baggage security
- go to the gate

This whole process can potentially take a long time. 3 hrs is doable but fairly risky on separate tickets with no onward protection.

Very good clarification and summary of what is needed in this instance. I personally wouldn't risk it but it is doable especially if they happen to have priority passport control, priority check-in and fast track at T3.

What an f'ing nuisance.

That's a consequence of the separate tickets. If this were a single ticket the OP would simply get off their arriving plane, follow the signs for connections to Terminal 3, take the airside bus to T3, clear security at T3, go to the gate and board. Easily done in 3 hours with plenty of time to spare.

The separate tickets mean that the checked bag must be claimed by the pax and re-checked. That's where the nuisance arises.

You are correct, but it would be nice if BA would check the bags through (especially when it is BA to BA). I know this will not happen, but to me it is just another reason to avoid BA whenever possible...

True, but from the airlines' point of view, it would also be nice if passengers get single tickets on one PNR for their journey instead of multiple PNRs.

This is their way of offering an incentive for desired behavior.

i agree so i've booked arrival night before. LHR hotel. comfortable departure the next day. We have zero status... just smartly used points to go all biz. But i think it's all too much of a risk for us. Might make it... might not.

thank you all very much! i've learned again.

Perhaps if BA stopped increasing the fares 2-3X for a single PNR, we wouldn't buy separate tickets. It doesn't cost an extra $2k to move my bags from one plane to another.

What points are you using such that you need to book separate tickets?

On AA, it will cost you the same amount of miles to do CPH-LHR-LAX as just LAX-LHR.