I booked an award ticket in J to Europe for this summer over the phone. The DL rep, who was extremely helpful, told me the only segment where F/J was not available was MKE-ATL. She said she was putting me in EC. When I went to check on my reservations on the DL site nothing in my seating zone was marked in red. I am thinking perhaps on some routes that EC means the first few rows of Y. I know this makes no sense but I can think of no other reason.