Many people have a fear of heights and haven't really had a seat on a plane before. These people don't know the manners that govern being on a plane in mid air and don't know how they should behave. There is a certain amount of ambiguity that rules their mind and they have no idea of how to limit it or combat it.
This guy here was travelling on an airplane for the first time and wanted to have a good sleep on the way. Since he was a very active sleeper, the guy didn't like being confined within the seatbelt. This is exactly why he started maneuvering around in his sleep and ended up being in this position. We are literally amazed that this guy can sleep in such a position. Seeing him makes us uncomfortable.