Which of the following is essential to document when planning an alternate airport?

• A. Alternate selection rationale and conditions under which it would be used.
• B. Weather brief for the day.
• C. Name of the controlling agency.
• D. Route distance to destination only.

Answer: (D)

When planning an alternate airport, you must document the rationale for selecting that alternate and the specific conditions under which you would switch to using it. This creates a clear, actionable plan: you know exactly why this alternate was chosen, what weather or fuel criteria would trigger a diversion, and how you’ll proceed if the destination becomes unusable. That documented criteria keeps decision-making objective and repeatable, which is crucial in flight planning and regulatory compliance.

Distance to the destination, by itself, doesn’t provide these decision rules. Knowing how far the alternate is from the destination tells you nothing about when you should actually divert, what weather minimums or contingencies apply, or how fuel and routing will be managed. A weather briefing and other details are important, but without the documented rationale and the conditions under which the alternate would be used, the plan lacks the actionable guidance needed during flight.