Originally Posted by
Avleen Vig
So if there is R inventory, is having the fare required to be booked in W or better? AIUI, W is the highest "deep discount coach" fare.
If you want to use a GPU, yes. If you want to use miles, there is no minimum fare class, but a hefty co-pay for lower fare classes.
Note that LHR-SFO is a tough upgrade and you're not likely to see advance R.