I have been platinum for several years. I normally fly 3 or 4 international flights to both Asia and Europe each year. Almost all are B fare. I try to use miles to upgrade every single time. In the last 3 years, I have been successful only once! The flights are often booked 4 -6 weeks in advance. Each time, I call the Gold/Plat line and inquire about upgrade availability 2 times/week. I'm always told that although I do have an upgradeable fare, there are no WBC seats left for upgrading.

NWA has a very generous frequent flier program in many respects, but not when it comes to international upgrades!