Have you tried politely asking them to move their legs?
In myFrom personal experience, most people who do this are either completely unawarethey might not know that they're doing it. I have unintentionally sat in seats with my legs spread rather wide. I have always moved my legs when asked. Sometimes this simply wasn't possible because the leg room was physically too small for my long legs.
As Imus said in their answer, or they are unawaresome might know that it's an issuethey're doing it but they don't feel like they're taking up too much room. Asking them "Couldwill usually make them accommodate you move.
If you want to sit down in an unoccupied seat that is being blocked by the person next to it, try something like:
Excuse me, can I sit here?
If you are already sitting down and the person next to you is taking up too much of your legsspace, please?" will often be met with a responseyou could instead try saying something like "Oh:
Excuse me, could you move over a bit? I don't have enough room.
An alternative solution
Move to another unoccupied seat if one is available, sorry"or stand somewhere. This might not be an ideal solution for you, and the situationbut it is resolvedthe best way to avoid conflict altogether.