NDPU has been oft-discussed on this forum in the various OLCI upgrade threads.
The broad consensus is that after a long enough period of not taking upgrade offers the flag will clear and you'll be eligible again.
As for why: the idea is to get someone used to the idea of flying business class, not to give elites upgrades or the expectation of the same.
https://www.flyertalk.com/forum/29850598-post410.html
Post from 2018 with prices and NDPU/regular flag. Others have mentioned seeing the NDPU flag on purser iPads.
Last edited by hhdl; Feb 10, 2023 at 2:56 pm