Originally Posted by
becket5
The invitation at BGI is in the form of a duplicate boarding pass with a rubber stamp in red confirming access to the lounge. I've never seen this anywhere else.
True, it's the only place I've seen it. I think it has two functions:
1) making sure that AA pays for that particular access (since the airlines share the cost of operating the lounge)
2) to prevent you from handing off your "invitation" to somebody else for use. However, since they don't check identification at the lounge, I see no reason why you couldn't give it to somebody else to use.