Originally Posted by
muji
My relatives will have a similar in-transit travel scenario at LHR.
So, the passengers collect their luggage at the baggage reclaim upon arrival at terminal 2, then go with all their luggage through customs (and also immigration, even though the passengers are just in transit), then take the Heathrow Express with all their luggage from terminal 2 to terminal 5. At terminal 5 they would need to check-in, and check in heir luggage, for their next flight.
Is this all correct?
Assuming your relatives have separate tickets for the flight arriving in T2 and the flight departing T5, and can't persuade the airline operating the arriving flight to through-check the luggage on to BA, then yes.
If the first airline is UA and there are separate tickets, it is policy not to through-check onto other alliances. Other airlines that use T2 may have more flexible policies, but you'd need to ask them.
The point is that in all airports I've ever seen that handle international flights, immigration comes before baggage reclaim and customs, so if you need to retrieve your baggage you have to go through immigration to get there. In the USA to make an international to international transfer you'd have to go through immigration and customs whether your baggage was checked through or not, and even if you had no baggage at all.