Howdy,

I was looking for R space on an upcoming flight and stumbled on some interesting thing.

When crawling for UA46 IAH-FRA on Feb/16 you get
J0 JN0 C0 D0 Z0 ZN0 P0 PN0 R0
and consequently: Business not available.

Surprisingly, when checking the reservation tab both me and a colleague are offered to purchase an upgrade - with an availability of 4.
This kinda confused me, as it seemed all the business buckets seemed empty.

On top of that: When checking for business availability via lh.com I can also find UA46/LH7600 with availability in J.

Anyone an idea, why they are not showing availability of any of the business class buckets in expert mode, not selling them... but offering paid upgrades?
... and, to which buckets do paid upgrades track btw?