Reply To: LHR airside transfer – T5 to T3 and back again

[Thegasman]

It’s theoretically possible. You need to get the airside transfer bus to T3 from T5.

The issue arises if you are marked as being in T5 on Fly (BA’s IT system) as you will then run into problems when you return to T5 later in the day. You would then need to find a suitably senior/experienced BA staff member to resolve this & they are not in abundant supply at the moment! If they get it wrong you’ll be automatically offloaded from your longhaul flight & won’t know till you get to the gate. You would also be a low priority for them so would potentially have a reasonable wait at T5 security (the security staff are not BA employees so can do nothing to fix this).

If you can access the transfer bus from the area where you emerge from jetbridge or bus from domestic flights then the process is much simpler as you won’t be marked as having entered T5 on Fly. I’m not sure if you can get access to transfer bus without entering T5 as I’ve not done it but I would guess you can. Look for purple flight connections signs. If you have to go up the ramp through the boarding pass scanner that spits you out in main T5A departure area then you would need to follow a different route the same as if you were originally departing T5.

In this scenario you have to get the train to T5C & stay on it at the end of the line so you then return to T5A in the arrivals stream where you can access airside transfer bus through flight connections. To return to T5 you again use flight connections stream from T3.

Note that you will need to go through security again at both T3 & T5 whichever way you access flight connections bus. You may meet some resistance from either security or lounge staff in T3. I’m describing what is technically possible (boarding pass scanners at T2 & T3 security are not programmed to automatically reject a T5 BP whereas T5 ones are in the reverse situation) but this is also not specifically permitted in any policy. If you ask a Heathrow agent for advice they will likely tell you that it’s not possible so very much a case of knowing what to do, not asking for help & hoping those you meet along the way aren’t having a bad day.

I’m summary, would I do this with a 9 hour layover? Yes if solo or with my wife who is fairly understanding of TP runs, ex EU’s etc. If I was with children or parents etc then I wouldn’t bother as it’s a bit of a schlep with no guarantees of success & a potentially major pitfall.