Flying MIA-MXP on 24 Nov 09 and for the first time transitting LHR from AA term 3 into the new Term 5for a BA (AA codeshare) flight.. Question is: What does this transfer involve? I assume AA will check me in all the way to MXP fronm MIA. Upon landing at LHR will I have to pass British immigration and customs or just immigration. Will I not have to claim bags. I know I will have to take the Heathrow Express (free I gather from reading BAA's web page) to Terminal 5 where I have to reclear security. I'm assuming there is no sterile connection from AA terminal 3 to BA terminal 5.
Also, my layover at LHR is 3 hours. If the connection involves clearing Bcustoms/immigrationWill I be able to walk around the central terminal area to visit it to see the progression of the remodelings to term 1 and 2?