Under what condition is an alternate airport not required?

• A. The weather within +/- 1 hour of ETA shows ceiling at or above 1500 feet above the lowest circling MDA and visibility at least 3 miles
• B. The weather within +/- 2 hours of ETA shows ceiling at or above 1500 feet above the lowest circling MDA and visibility at least 3 miles
• C. There is no weather data available for the area
• D. Alternate weather minimums are not authorized for that airport

Answer: (A)

In IFR planning for Part 135 operations, you only skip having an alternate if the forecast at your destination meets a specific safety margin within a close window around your ETA. The required margin is that the weather is at or above 1,500 feet above the lowest circling minimum and visibility of 3 miles, within one hour before or after your estimated time of arrival. This gives enough vertical and horizontal visibility to complete a circling approach safely at the destination, reducing the need to designate an alternate. Extending the window to two hours, or having no weather data, does not meet the rule, and there would still be a need for an alternate. The idea that alternate minimums aren’t authorized isn’t correct in this context, so the best condition for not needing an alternate is meeting that 1-hour window with the specified margin.