Should not be a problem from the US. I had some issues coming from AMS to PDX on Delta the other day though where the KLM agents gave me grief because I was not listed. Got on in the end and I have a mail in to our jumpseat coordinator right now regarding both jumpseating and ZED travel on Delta. I'll let you know if I learn something else. I myself might be going on Korean Air in early August, any problems with ZED travel on your side?
Fred