My first reaction, looking at your desired destinations, is that they are all easy to get to via Star Alliance airlines. Now, I don't have experience with United's mileage program and stop rules, but I am familiar with Aeroplan (Air Canada's FF program, at least until 2020 ). Doing some playing around with the AE website, this itinerary should be doable IF you fly to and from Athens, and buy a separate flight to Santorini. The points required for Business class would be 150,000 each, and both your AMEX and SPG points can be transferred to AE, so you have plenty to make this happen. For more info and to ask for help putting together an itinerary, check out the Aeroplan board, and specifically this thread: The Complete Newbie Guide/FAQ to the Air Canada Aeroplan Mini-RTW