Delta's portfolio of international routes from JFK and ATL to Europe are a rare opportunity for an airline with strength to one part of Europe to consolidate its position to all of Europe. If LHR is your strength then why not fly from Moscow in the east to Paris. Delta offers this strength to AA, then who knows, JetBlue could seize the assets to establish itself in the Atlantic market. To say Delta's JFK routes don't have value is wrong and naive. While its fairly easy to fly to Paris and Frankfurt from most American cities, it would take years to build a system like Delta's, especially from America's premier international airport, JFK.
