What is an alternate airport?

An alternate airport is defined as an airport that is specifically designated for use in the event that the primary airport becomes unavailable for landing. This situation can occur due to a variety of reasons, such as adverse weather conditions, unforeseen mechanical issues, or other circumstances that could prevent a safe landing at the primary location.

In aviation regulations, particularly under instrument flight rules (IFR), having an alternate airport is crucial for flight planning and safety. It ensures that pilots and dispatchers have a contingency plan in case unexpected changes arise during the flight. The designation of an alternate airport helps ensure a safe landing can still be achieved, aligning with the fundamental principles of risk management in flight operations.

By contrast, the other options presented do not accurately reflect the purpose or definition of an alternate airport. An airport that is not operational during certain hours does not serve as an effective alternate, as it might not be accessible when needed. An airport only used for emergencies does not encapsulate the broader usage and pre-planned nature of alternate airports. Lastly, an airport exclusively for passenger check-in does not relate to operational readiness for flight, as its function is unrelated to the landing process.