I'd say it also depends on the number of courses being served. Sometimes it'll be served before the main dish, sometimes with, and sometimes it is the main course (the one I dislike the most)

AS has several different variations... on mid-range flights, they now serve the salad with the main course, and on trans-con flights it becomes a separate dish.

I've never traveled internationally yet (except for walking across the boarder into Mexico once) so I have limited experience with different cultures...it is weird that salad would be eaten last.