I will narrate an incident. I was in a 2 hour flight at 6 AM a few months back. The person sitting right next to me came to his seat, put on his seat belt and went to sleep even before take off. He started snoring within minutes and his snoring was so loud that people in 3-4 rows behind and ahead of us were turning their heads and trying to see who was snoring so loud. After take-off the stewardess woke him up and whispered in his ear that he is disturbing other passengers. He seemed very embarrassed and tried hard to stay awake for the next 15 minutes but then could not help himself and dozed off again. Within minutes the snoring resumed and continued till we landed! Everybody else's sleep was disturbed :)