Not sure if it's an old wives tail but many moons ago in the j/s of a QF 767 was chatting to the F/O who used to fly night freight on the east coast and he was saying he'd fallen asleep in a Seneca a few times. Anyway he digressed and said that when Norfolk Airlines used to operate the King Air that they used to use it for night freight and one night when he was flying the Seneca centre kept calling and calling him with no response, he overflew SY at FLT240 and woke up. Not sure how true it was, but certainly possible I guess!