Probably 20 yrs ago from LAX-MPS. I was in my best suit and checked in early on NWA in coach - probably a 757. When I double checked my seat with the gate agent she told me there was a plane change to a 747. I told her I had never been upstairs in a 747 and hoped I could try that. She told me the upstairs wasn't open. About 20 minutes later she called my name and handed me a boarding pass to First Class upstairs.

Turned out it was a brand new 747. Boy did I enjoy that ride!