I've had a period that I used a very decent sleek black backpack. I was a few years younger, what did I know
Now I'm back to handbags. The image of a pilot's unifom, or any other suit for that matter, and a backpack just does not go well together, especially the huge schoolboy bags that some prefer to carry around both shoulders. (If you have to use a backpack, at least just hang it over one shoulder!!)