Exiting and Entering the U.S. and Hungary Without a Valid U.S. Passport
American citizens must possess valid passports in order to enter and exit the U.S. and most foreign countries. Airlines are responsible for ensuring that passengers hold valid passports and generally will not allow passengers to board flights without them. Bear in mind that the U.S. Embassy cannot intervene when this situation occurs.
If your U.S. passport has been lost or stolen while traveling in Europe and you are en route to Hungary, we strongly recommend that you visit your nearest U.S. Embassy or Consulate to replace your passport before coming to Hungary. The U.S. Embassy in Budapest is not able to arrange entry into Hungary for U.S. citizens who arrive without proper travel documents.