What is an "alternate airport"?

An alternate airport is defined as a specific airport designated in the flight plan for landing if the primary destination airport becomes unavailable during the flight. This is a critical safety measure, as it provides an alternative option in case of unforeseen circumstances such as weather conditions, emergencies, or operational issues that prevent landing at the originally planned airport.

Choosing an alternate airport is an integral part of flight planning, especially for long flights, where the chances of encountering issues at the destination airport may increase. Regulations often require that an alternate be designated under certain conditions, like when the weather at the destination doesn't meet minimum visibility and ceiling requirements.

In contrast, the other options do not accurately capture the definition of an alternate airport. An airport chosen solely for emergency landings does not necessarily serve as a planned alternate for operational purposes. Similarly, limiting an airport to only domestic flights or defining it strictly as a secondary refueling point does not encompass the broader operational role of alternate airports in flight planning.