What Causes Swollen Feet?

I went home(Philippines) last November, and I have notice that my feet is swelling. Well they said its because of sitting more than 14 hours in the plane but it didn't subside until after 3 days that I arrived back here in Canada. It happened again this kind of situation when i went home 4 years ago. I have stayed there for 3 months. As soon as I enter a cold place when I checked-in already at the airport I've noticed that the swelling is subsiding.