Originally Posted by
HalconBCN
In my case, the conversation went like.
Me: Hello, here is my boarding pass.
Agent (looking at DL paper boarding pass): Where are you flying to?
Me: I'm flying with Delta to Detroit.
Agent: Oh OK, unfortunately you can only use this lounge if you're flying Delta in business class.
Me: I am Flying Blue platinum, look, this is my boarding pass on the KLM app. It's a KLM code share flight.
Agent *few seconds pause*: Oh OK, I see. KLM! Fine. Welcome in to the lounge!
I understand you were booked under KL code-share and this seems to be what convinced the lounge agent. But, even if you had been booked under DL code, you should have lounge access as a FB Elite+ travelling internationally in Y and even if this is a contract lounge. Skyteam site is very clear about this rule. Only DL Elite+ members are excluded in this case (Y, contract lounge). Look here :
https://www.skyteam.com/en/lounges/