What minimum coverage must the weather forecast provide for alternate aerodrome planning?

The minimum coverage that a weather forecast must provide for alternate aerodrome planning is indeed 30 minutes before and 60 minutes after the estimated time of arrival (ETA). This timeframe is crucial as it allows pilots to assess weather conditions that could affect the alternates along their route and during their approach.

By requiring this specific time range, it ensures that pilots have adequate information to make informed decisions about their destination or alternate airfields. Weather can change rapidly, and having forecasts that cover this broader time span helps pilots prepare for the possible conditions they might face upon arrival.

This choice correlates with best practices in aviation safety, ensuring that the forecast is relevant to both the arrival and any necessary diversions that might occur due to adverse weather conditions at the intended destination.