Ah, those PanAm memories! I flew regularily with them throughout the 80's. I didn't have a chance to fly in their glory days, but the early 80's weren't bad. They had a womderful upgrade policy (yes, all fares were upgradable as far as I can recall). Besides that, platinum members got one class upgrade when the ticket was purchased. I bought a $129 transcon economy ticket which was upgraded to Bus at purchase. I then managed to talk myself into an upgrade at check-in in LAX, so I flew first for $129. Not bad! Their transcon breakfast was something to die for!

IIRC Platinum (their highest level) was something like 50,000 miles per year, so it wasn't too difficult to achieve. But another poster was correct in that you had to get to a certain level each year to qualify for the next year. If you didn't qulify, you lost your miles.