A couple years ago, I was flying ONT-LAX-SYD-PER and got hung up at ONT, as LAX could not give the puddlehopper clearance to land (it's a great 1000 miles and the best view of the LA basin, but that is the occasional risk you run). Got to LAX and the 744 - and my confirmed upgrade - was pulling out. The gate agent told me that NZ's flight to SYD(yes, that many years ago) was running about three hours late and she would put me on that. I walked across the parking lots to T2 and presented my old paper coupon - which, to my great surprise she accepted and put me in the upper deck C class.

Now that NZ has outfitted themselves with the new VS kit (and now that there are no paper upgrades) that would never happen, but it has happened at least once