Originally Posted by
fassy
And not forget to apply the lottery factor X which is the likelihood of the requested upgrade to clear. And what X is? I guess nobody knows for sure....
The best rule is: If you want to travel in a specific class of service, buy (be it with cash or miles) a ticket for that cabin class and do not rely on upgrades.
True, though I think this can be done quite reasonably when checking whether there is I space for partners (or M&M members if M&M miles are used).
I know that this isn't exact as there can be a difference in the award and upgrade space, but it's at least a half-decent indicator :P