When traveling internationally, it is typically a requirement to present a valid passport. However, there are a few exceptions where specific travel arrangements allow for certain flights without a passport. Here are a few examples:

1. Pre-clearance facilities: Some airports in the United States offer pre-clearance facilities, where passengers complete immigration and customs formalities before departing. This allows for domestic-like travel upon arrival in the destination country, and passengers can travel without presenting their passport at departure.
2. Trusted Traveler Programs: Trusted Traveler Programs, such as Global Entry in the United States, allow expedited processing for pre-approved, low-risk travelers. While a passport is still required for international travel, participants in these programs may experience streamlined security and immigration procedures.
3. Closed-loop cruises: When taking a closed-loop cruise, which starts and ends in the same U.S. port, passengers may be allowed to travel using a birth certificate and government-issued photo identification instead of a passport. However, it’s important to check with the cruise line and destination country requirements, as some may still require a passport.

It’s essential to note that these exceptions are specific cases, and in general, a valid passport is required for international air travel. It is always recommended to have a passport when traveling internationally to ensure compliance with immigration regulations and to have proper identification in case of unforeseen circumstances or changes in travel plans.