In 2026, the answer depends on your destination and the specific airline's policy. For domestic flights within your own country (e.g., flying from New York to Los Angeles or Delhi to Mumbai), you do not need a passport to book or board; a standard government-issued photo ID is sufficient. For international flights, many major airlines and booking platforms (like Expedia or Skyscanner) allow you to reserve a seat and pay for your ticket using only your legal name and date of birth. You can then add your passport number, expiry date, and country of issue later via the "Manage My Booking" section or during the online check-in process (usually 24–48 hours before departure). However, some carriers—particularly those flying to the U.S., China, or certain Middle Eastern countries—may require passport details upfront at the time of booking to comply with "Advance Passenger Information" (API) regulations. If you are waiting for a new passport, you can generally book the flight first and update the details once the document arrives, as long as the name on the ticket exactly matches the name that will appear on the new passport.