These appointments are only for people who have urgent travel that already exists. You HAVE TO already have a flight itinerary in your name booked and printed out. Otherwise your case isn't emergent. They do verify your flight itinerary with the airport. They do not allow walk ins. They verify appointments downstairs before you're allowed through security.
You will be turned away without a appointment, with a appointment yes you can get your passport the same day. As for the proof of travel as long as you are able to show a flight itinerary if you are flying overseas or a hotel if you are traveling by car to Mexico/Canada
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