VAPilot has it right about the P&W 757-300s. They just do not have the capability to do transatlantic with any viable payload, especially in the winter months. NWA 757-300s are etops certified and operate from the west coast of the USA to Honolulu, Maui and Kona. NWA's plans to operate 757s to Europe involve certifying a subfleet of 9-10 757-200s for etops, adding winglets to them and increasing their certified max take off weight substantially in order to make them viable for flights from such places as DUB/MAN to DTW year round. So, in a nutshell, I doubt very much that you will ever see NWA 757-300s over the Atlantic unless an aircraft substitution is required, and even then it would probably require a fuel stop in YYR/YQX or similar on a westbound leg.