Question re connecting @ LHR with NEW BA slots
 

I have a question relating to a hypothetical scenario where BA has bought BMI and thus has more slots at LHR, but no space left at T5 and so adds destinations to other LHR terminals (3 for instance).

In such a scenario where BA switched its Orlando flight to LHR from LGW and I were travelling BA from BRU to MCO, arriving T5 (from BRU), departing T3 for MCO and my baggage was ticketed to final destination MCO, what would happen if I exited T5 via and took Heathrow Express to T3 and checked in there?

Would it be a problem or not?

If you have a through ticket, you got to inter-terminal transfers and they arrange the txfer. happens every day. Check the LHR web site and your ticket (if you have one).

If you have separate tickets then you will have to enter the UK, pick up your baggage, take the train to T3 and start all over again.

With a through ticket you would probably be given both boarding passes at BRU and be expected to use the airside transit options. If you choose to exit landside and use the train between T5 and T3 you won't need to check in again in T3 simply present your boarding pass at T3 security. If you don't get a boadring pass for LHRMCO at BRU that might cause a few scratched heads when you checkin in T3 but I don't see anything insoluble.

In the end I see no reason why you are barred from doing it. The only possible problem might be if the time taken means you miss the flight from T3; if they discover you've been landside they might be difficult but I think that's unlikely.

I know transfers happen everyday, thanks. My question is what if I decided to exit T5 and re-enter T3? I.e. make my own way there using Heathrow Express rather than the awful Heathrow transfer buses which take ages. Immigration and customs and security is not a problem.

Many people do this every day, having experienced exactly what you describe, as well as meeting friends who live in London etc landside for a brief visit.

For an on-line BA, or BA to Oneworld connection they will check the bags through even with separate tickets.