Originally Posted by
RobOnLI
But it does mean PN is being hidden. It also means there's an algorithm that runs whenever an RPU/GPU request is made to see if this hidden bucket is greater than 0.
The only reason I can think UA actually hides the PN bucket for RPU/GPU for GS is so that 1Ks don't pull the inventory on a YBM fare immediate upgrade. They wouldn't have access to the hidden PN bucket. Only someone applying an instrument would.
It's all controlled by Inventory Management algorithms - I've long used P fare bucket availability as a proxy for PN likelihood of clearing. In every single case when P has been available my instrument upgrade has cleared into PN within 7 days, and on Domestic itineraries it is often instant as you describe. I have not yet missed an upgrade when P available at booking.
I don't think there is a "hidden PN bucket" as such ... in a prior discussion during a UA Willis Tower tour event, they explained to me it effectively is a product of adding to the waitlist, the waitlist system hitting inventory management, checking who else is on the waitlist, deciding based on rules, and then converting inventory from F/J to PN and clearing ... but who knows?