Steve,
Years ago once when I was down in L.A. working, they had a news cast on and were following one of the big UPS planes. It flew right over LAX and on out into the ocean and they couldn't contact the pilots. Finally one of them came on the radio and wanted to know where they were as all he could see was water. They gave him directions and once they got headed back to land they started questioning him. Turned out both the pilot and co-copilot had been having a few before the flight and had gone to sleep. I think they were about 3 minutes from being past the point they would have have had enough fuel to get back to land.
Ron