Originally Posted by SAT Lawyer

Does anybody know what happens when I use the "WorldPerks mileage upgrades" feature in the drop-down "Change or Upgrade Reservation" menu of an existing reservation at nwa.com? What is the consequence if I check the box and click "Upgrade Existing Flights" if upgrade inventory exists on some, but not all of the flights? Will nwa.com let me know or will it deny the upgrade effort entirely without breaking down whether inventory was available on none of the flights or just some of them? And will I automatically be upgraded having checked the box and clicked the "Upgrade Existing Flights" button if some or all of the applicable flights have inventory or will I have a further opportunity to see which flights have inventory and which do not before making my final decision? What I don't want to have happen is that I get stuck with a mileage upgrade if only the intraEuropean KLM segments have upgrade inventory, but the transatlantic segment does not. Is this a potential danger?