You've probably heard the old "no shirt, no shoes, no service". It applies to airlines as well.
What had me thinking about this is the fact that there have been passengers removed from flights because of a shirt deemed "offensive", or a mini skirt seen as too mini.
But could you travel barefoot? Apparently not, as many airlines have security policies regarding, shall we say, passenger hygiene.
Policies may be worded differently but the general idea is that because of safety and security reasons all passengers are forbidden to travel barefoot. Airlines have the right to refuse travel to a passenger trying to travel barefoot. To be clear then - footwear is mandatory for "service".

