Apologies if this is answered somewhere else but I have been bumbling around in the stickys now for an hour and cant find the answer..!

I have a trip in May SIN-NRT-ORD-MCI-ORD-HKG-SIN booked in economy (booking class:B) and which I have applied to upgrade to business at 15,000 miles each way.

Right now only ORD-MCI has cleared and 5 of the 6 legs are waitlisted . Though I expect this to change over the weeks to come, I am just curious if I end up with only partial upgrade availability near the date of travel and dont want to blow 15,000 miles for 1 or 2 sectors out of 3, and I am also not really keen on the nail bititng "will I or wont I" gate tension.

So prior to travel are these upgrade requests reversible. Can I just call MP and cancel the upgrade request and ask them to return the miles.?

Thanks for any info