This may seem an odd question, but how aware are people of how long they are asleep on flights? One leg I had on fri/sat was 11 hours, all night. I must have slept a fair amount as the first seven and some hours went by quickly, and then the last three and a bit hours went by at a crawl. Even if I'm not asleep, I do try and rest with my eyes shut as mock sleep as I have read (Stanford U. sleep unit) that 'pretending to sleep' actually has value if you can't sleep. I have some memories of a meal going by, but who knows how many hours I slept.

I'd really like to know, but have no idea. Anyone else have this problem?