Originally Posted by terenz
I am pretty certain you have to be flying a OW airline on that day to have access to an OW lounge ("own" airline or otherwise). You certainly don't get to access an OW lounge if you're flying a ST or *A airline that day. The only difference between top-tier (emerald) and middle tier (sapphire) in OW is which class lounge you get access to (first and business respectively).
The BA business lounges are open to Gold members irrespective of the airline they're flying. The
BA web page is less than clear about this, but I remember this having come up in the BA forum. I'm not sure how other OW carriers treat their Golds, but it does look like general OW business lounges are not open to BA Gold unless they're flying OW.
Ah, found the
BA thread on lounge access.