Originally Posted by
Kmxu
To accept an instant upgrade, you should try both the app and the website, though the app tends to work better. I had some trouble with the EWR-IAD instant upgrade, but it worked a day later. I’m not sure why this route is so problematic.
I just booked UBN-NRT in M class. There was no instant upgrade option on the website but it was available in the app, which worked fine.