The openings of the top compartment and the side compartments towards the top are just barely wide enough to fit an American passport if it doesn't have a plastic cover. Even then, the passport can be damaged by frequently brushing against the zipper. It is also not easy to get the passport out fast. However, several American passports will fit into the bag in the top and side departments if necessary.  Either zipper opening is too small for a European passport book which is hardcover and 2 mm wider and longer than an American passport book.  I find the bag not useful since I don't want to struggle getting out my passport every time. The idea was to get a bag for easy and quick access and storage between checking in, security check, customs, etc.  I will look for another bag.