There is a way to add miles to a Europe trip from DFW without adding much (if any) cost. That is to "slingshot" out of a west coast city such as LAX or SFO. For example, DFW-LAX/SFO-FRA/MXP/etc-LAX/SFO-DFW. It can turn a 10K mile itinerary into a 16K mile one easily.