Hello,
I tried searching for this but couldn't find any anec-data.
JAL has an airport upgrade offering, listed at
https://www.jal.co.jp/en/jalmile/jal_up_today.html#info.
This service is to apply for JAL International Upgrade Award upon check-in at the airport on the day of departure. This service can be used when a seat is available in the next higher class of service than that of the purchased ticket.
You can pay fewer miles to upgrade day of flight instead of earlier. The savings vary.
Has anyone tried to get one, and has it succeeded? Would love info on routes/experiences. Thanks!