Which requirement must be met by an alternate airport for IFR flights?

An alternate airport for IFR flights must have weather reporting at the time of arrival to ensure that pilots can safely land at that location if the primary destination becomes unavailable. This requirement is crucial because it provides the pilot with current weather conditions at the alternate airport, including visibility and cloud cover, which helps assess whether a safe landing can be executed. Without up-to-date weather reporting, a pilot cannot make an informed decision regarding the suitability of the alternate airport, potentially compromising safety during flight operations.

The other options do not reflect essential requirements for an alternate airport under IFR. For example, while having multiple runways may be beneficial, it is not a strict requirement for an alternate airport. Distance limits from the destination are often specified but depend on the type of flight and regulations in place, rather than being an absolute rule applicable to all IFR flights. Finally, the availability of an approach plate, while helpful, is not strictly required for an airport to be designated as an alternate. These factors highlight the importance of weather reporting as a critical element for ensuring safe landing options under instrument flight rules.