This is incredibly helpful. Thank you for taking the time to write it all out. Your observations actually confirm the main reason I haven't shipped UXP yet: the logic looks simple on paper, but real-world behaviour has all kinds of conditional states, UI quirks, and legacy edge cases that Flying Blue doesn't document anywhere.

A few things I'm taking from your breakdown:

Retroactive UXP visibility after qualifying for Platinum
Super interesting. Even if it's a display glitch, it suggests the backend might store UXP-eligible events even before the member reaches Platinum. I definitely won't assume retro-crediting in the engine, but I'll build the structure so it could be supported if confirmed.

UXP qualification period alignment
This is where I'm slightly less certain. My understanding is that since recently, UXP cycles now align with your regular qualification period once you're Platinum and not the old Jan-Dec calendar year. But documentation is scarce, and I haven't been able to confirm this definitively. If anyone has firsthand experience with how their UXP cycle timing works post-Platinum, I'd love to hear it.

First-time Ultimate qualification not deducting XP/not creating surplus
This is gold. I hadn't seen this documented anywhere. I'll treat first-time Ultimate as a 'soft promotion' where XP logic is suspended once and only UXP carries the state forward.

Rollover after Ultimate = identical to XP (−900 + surplus)
Perfect. This simplifies the state machine once the member is already Ultimate.

The AFKL flights showing UXP for pre-Platinum segments
I'll treat this as a front-end artifact unless more people report it, but it's definitely worth keeping in mind.

If you don't mind, I'll incorporate your notes into the UXP engine design doc so the implementation matches how the system behaves in practice rather than how Flying Blue describes it (if any).

Thanks again!