<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by DL Platinum:
Guess I need to avoid the hub to hub runs if I want to be upgraded!</font>
Well, if you want to do a mathematical approach...
Since NW does wingtip flights between hubs with different aircraft types, maybe tend toward ones with a higher F to Y ratio. I'm too lazy to do the math
but there's a ratio difference in a 320 vs. a 757 vs. a DC9.
In my years as mid and upper tier, I've had decent luck on MSP-DTW and occasional MSP-MEM... although it's been a year or two since I've flown those routes.