For an alternate airport to qualify, the worst forecast weather for the ETA +/- 1 hour must be at or above?

To determine whether an alternate airport qualifies based on weather criteria, it is essential to refer to the specific requirements outlined in aviation regulations. The correct answer is based on the minimum forecast weather conditions for an alternate airport, which states that the worst forecast weather for the estimated time of arrival (ETA) plus or minus one hour must be at or above certain minimums.

The correct requirement specifies that the alternate airport's weather must meet or exceed 600 feet of ceiling and 2 statute miles of visibility in order to qualify. This is in line with regulatory stipulations which aim to ensure that weather conditions at the alternate airport are adequate for safe operations, particularly if the primary destination becomes unavailable for landing upon arrival.

In this case, the provided answer accurately reflects the standards necessary for an alternate airport. It allows for successful visual or instrument approaches and ensures that pilots have enough information to make informed decisions during flight planning. The specific minimums are critical for maintaining safety during unpredictable weather conditions.