Originally Posted by UKtravelbear

Just for fun if there were to be any terminal changes etc I would see them being in this order of priority but depending on issues such as 'completing' T5C and improving facilities / shops / lounge and then building T5D a different order of practicality

1 All BA flights from T3 move to T5 - simplifies BA ops at LHR. Also reduces costs such as not operating T3 lounge,other staff savings removing duplicate functions, and eliminates lounge hopping (I can hear the wails of complaint already lol). Improves passenger connection experience.

2. AA move from T3 to T5 - eliminates the need for intra terminal transfers, reduces connection time and improves passenger experience, reduced airside traffic (so benefits the environment / saves HAL money). Chance for remaining OW airlines to reconfigure locations - MH/QR from T4 (which could happen if just BA move from T3). AA really need to move en-masse as they won't want split their ops between terminals.

3. Other OW airlines depending on size and numbers of connecting pax to/from BA but there could be a case of retaining T3 as the 2nd OW base

4. EI move to T5

I'll put my crayons away now!