What are "alternates" in flight planning?

In flight planning, "alternates" refer to secondary airports that a pilot may divert to if the planned destination becomes unsuitable for landing. This can happen due to various reasons such as unfavorable weather conditions, technical issues with the aircraft, or other unexpected events that make it unsafe to land at the original destination. The intent behind designating alternate airports is to ensure safety and readiness, allowing the flight to continue safely in case of such unforeseen circumstances.

These alternate airports are chosen based on their proximity to the intended route, available services, and appropriate facilities for the aircraft. The other options represent different concepts that do not relate specifically to the definition of alternates in flight planning. For instance, airports with extended services may be beneficial but do not qualify as alternate airports unless they meet the criteria for diverting from the main destination. Therefore, the correct understanding of alternates is critical for effective and safe flight planning.