Originally Posted by
dannieboiz
When I book flights with MVP upgrades, I usually get instant upgrades but when I selected mileage upgrade, I don't get any indication that I'm eligible for F upgrades during check out.
I've followed the process to use a guest upgrade but not a mileage one; I'm going to assume the process is similar.
For GGUs, you basically have an option on the reservation page after the reservation has been made that says something like 'click here to use a gold guest upgrade'. I hypothesize that if you're in an appropriate fare class for a mileage upgrade to work then it would be something similar.