I’m soon flying HND-LHR in Business on a D class fare. On the website it gives me the option to upgrade to First for 48,000 miles, but no cash or bid option.

I remember years ago, some regional JAL flights within Asia would offer cash upgrades from Economy to Business at check-in ( ex; PEK-HND for 50,000yen).

I was hoping of having a similar option for upcoming flight to London. Has anyone been offered cash upgrades with JAL at check in?