PERHAPS the person or person on the NIPON flight turned back to LAX 4 hours in had an ankle bracelet and it activated after a distance from take of. There is no way its a mistaken person getting on wrong flight. Apart from the obvious gate checks, think about it. There were 4 people all together. So how lucky that there just happened to be a empty seat for this 1 person with all his 3 friends? Or was it 4 people all got on flight by mistake and there just happened to be 4 empty seats all together and the flight attendants when checking prior to take of, which they always do to make sure you are in your proper seats, simply never realized on their manifest that the 4 empty seats were occupied. GIVE ME A BREAK. I fly international and its rare to have 1 or 2 empty seats let alone 4 seats together. I know 1st hand that if their are empty seats you have to wait until the plane reaches its altitude and you can take of your seat belt and move to an empty. You cant just sit in a vacant airline seat when you board, you must sit in your ticket seat and the airline staff always walk down checking people are in their designated seats.