Originally Posted by
xliioper
However, this conflicts with Amex Plat T&C's on Amex website which says either DL marketed or DL operated is acceptable (according to DL Sky Club access page, this is only the case for the DL Amex Reserve card and not Amex Plat). So you may get in with DL marketed, KL operated flight, but KL marketed and operated would probably definitely be a no.
The Amex Plat T&C's also say: "For the most current Delta Sky Club access and pricing policy, please visit Delta.com/skyclub", which suggests that the access policy published by DL supersedes the Plat T&C's (though I suppose one might have success at getting some MR points thrown their way for a rejected attempt to visit on a DL-marketed, KL-operated flight).