Originally Posted by
IAH-OIL-TRASH
This is NOT possible. You can upgrade on ANA to Business only from the two highest fare buckets of ANA's Premium Economy (equivalent to UA's O or A fares). If you buy an economy ticket for an ANA flight, you will stay in economy.
its certainly possible. Buy United economy ticket operated by ANA. Call United get them to change the flight number to ANA. Then use plus points to upgrade.
the question is nuanced, how to search and see if the upgrade will be available on ANA BEFORE buying the ticket and using United’s Plus points. United system only tells you availability after purchase.