I booked a trip to Costa Rica on CO in August and as a silver elite with NWA I asked if I could upgrade using miles. The first agent said the fare wasn't available but the second time I called the agent looked for a long time to find an "upgradable" fare. She found a fare (which was five hundred dollars more per ticket over a coach ticket!) and I upgraded using fifteen thousand miles each way. After it was booked and I received the e-ticket via the interent, I noticed it is an "R" fare. On NWA web site it states all the eligible fares on Co that count for elite status and "R" wasn't one of them!! Will NW recognize the "R" fare as another ~ such as Z??