Dirty and Smelly
Feet are generally something that people don’t like to see on a flight, and that is for good reason, most people spend hours walking and waiting before they board the plane. Now imagine having someone take off their socks and putting their feet on your armrest, which is definitely not ok.\
On the other hand, we as outsiders looking at this picture, we can’t help but laugh at the OP’s expense just a tiny bit. It would be even funnier if someone decided to tickle this person, and not stop until they apologize for putting their feet on the armrest.