"There have been some close calls over the years. The most famous being the UA flight that landed at WLG when they realised half way to CHC that they didn't have enough fuel for a missed approach at CHC or to get back to anywhere else that could take them."
This is interesting. A good few years ago I was up in the front office of a Singapore Airlines 747 enroute Singapore to Auckland. As we were taking in the dawn over Sydney, both Auckland and Christchurch were closed due fog but expected to open by the time we got there. My recollection is that we were carrying Sydney as an alternate (but wouldn't bet my left ball on that).
I asked the Captain if we could get into Wellington, which was open. He got out the books and a few minutes later said
"We can get into there OK but getting out again won't be fun".
Dr