If you book a flight but do not choose specific seats, the airline will typically assign seats to you automatically. The exact seat assignment process can vary depending on the airline and their specific policies. Here are some common scenarios:

1. Random Seat Assignment: In many cases, if you don’t select seats during the booking process or at a later time, the airline’s system will automatically assign seats to you. These seats are usually chosen based on availability and may not be adjacent to other members of your travel party.
2. Seat Selection at Check-In: Some airlines allow passengers to select seats free of charge during the online check-in process, which usually opens 24 to 48 hours before the flight departure time. If you haven’t chosen seats beforehand, this can be an opportunity to select seats based on availability.
3. Assigned at Gate: In rare instances, particularly for high-demand flights or when the aircraft is nearly full, the airline may not assign seats until you reach the gate for boarding. At that point, the gate agents will allocate seats to passengers based on the remaining availability.

If you have specific seating preferences, such as wanting to sit with travel companions or needing a specific type of seat (e.g., by the window, in an aisle seat), it is generally advisable to select seats as early as possible. Many airlines offer the option to choose seats during the booking process or through their website, mobile app, or customer service channels.

However, it’s important to note that seat selection policies and fees can vary across airlines. Some airlines may charge an additional fee for preferred seats with extra legroom or better amenities. It’s recommended to review the airline’s policies and any associated costs before making a decision.

If you have concerns or specific requirements related to seating, such as medical needs or accessibility considerations, it is advisable to contact the airline directly to discuss your situation and request assistance.