In the end he didn’t cheat anybody because he got caught. And to be fair if he had simply asked whether it was possible for him to take the business class seat then I would say fair enough.
However by just taking the seat and pretending it was ok he tried to cheat all though who had paid for the business class seat and also all those he tried to leave behind in economy. All people who understood that they had paid for a certain level of service.
It’s not like the empty seat he attempted to sit in was a like-for-like swap with his original seat. When buying his ticket he agreed to a level of service and comfort and made a transaction based on this. Then upon boarding the plane he tried to alter the deal after it had already been agreed upon.
However as I mentioned, I am torn between admiring his bravery in attempting to try his luck and him trying to cheat those around him.