Originally Posted by
LucWise
No need to worry, you should be fine. I'd recommend taking printed copies of your reservations with you that include record locators just in case.
Agreed. I've done this many times where I had one ticket US-LHR on AA and a separate ticket LHR-XXX on BA. The AA counter was always able to check me through (I always brought printed copies of both itineraries and locators to make it easy).
This also worked the other way around at the BA counter coming back to the US.