The requirement for an alternate airport is based on weather forecasts within what time window relative to ETA?

The requirement for an alternate airport is based on weather forecasts within what time window relative to ETA?

• A. One hour before ETA to one hour after ETE
• B. Two hours before ETA to two hours after ETA
• C. Only at ETA
• D. During the entire flight

Answer: (A)

When planning an alternate, you must be confident the weather at that airport will meet landing requirements not just at a single moment, but for the time you’re likely to use it. The forecast used for the alternate needs to be valid from about one hour before your estimated arrival to about one hour after your ETA. This window covers the period you’d actually be approaching and landing at the alternate if you have to divert, accounting for small timing changes along the way. Choosing this window keeps the assessment focused on the critical moment of landing at the alternate—neither too narrow (only at arrival) nor unnecessarily broad (every moment of the flight).

When planning an alternate, you must be confident the weather at that airport will meet landing requirements not just at a single moment, but for the time you’re likely to use it. The forecast used for the alternate needs to be valid from about one hour before your estimated arrival to about one hour after your ETA. This window covers the period you’d actually be approaching and landing at the alternate if you have to divert, accounting for small timing changes along the way.

Choosing this window keeps the assessment focused on the critical moment of landing at the alternate—neither too narrow (only at arrival) nor unnecessarily broad (every moment of the flight).