I'm not sure there is a clear rule....I've been trying to upgrade to F on EK302 (DXB to PVG) for weeks (departs Saturday) but there's no availability even though Expert Flyer shows only one seat in F currently booked.

Whereas EK002 was pretty booked up in F, but there was an upgrade seat available (I took it).

Would be great if someone can help shed light on this, but based on previous posts I'm not sure anyone can!

Can someone see the booking types available in the above flight?

Thanks in advance