Originally Posted by
rossmacd
The best way (if AA refuse to short check) is to head to flight connections desk in T5. At this desk, tell the agent you are not travelling further and you wish to retrieve your bag. You do not need to give a reason/excuse.
If the OP takes this approach, will the agent not make some sort of note or take some action to cancel the remainder of the OP's booking? I'd have thought this is quite a risky strategy! As far as I can tell, the OP still wants to travel onward to IST, just without one of their bags.