What type of situations would typically require an alternate airport?

The requirement for an alternate airport is commonly influenced by weather conditions because adverse weather can significantly impact a flight's ability to land at its intended destination. If forecasts predict low visibility, fog, heavy precipitation, or other adverse conditions at the primary destination, preparing for an alternative landing site becomes crucial. This enhances flight safety and ensures that crews and passengers have a backup in case landing becomes impossible due to poor weather.

In contrast, scheduled maintenance typically occurs on a predetermined schedule and does not change the flight plan, while emergency landings are often unexpected situations that require landing as soon as possible, often at the nearest available airport rather than a planned alternate. Aircraft serviceability relates to whether an aircraft is functioning correctly, but it does not directly dictate the need for an alternate airport unless directly linked to weather scenarios affecting landing at the intended destination.