A second alternate is required when which condition is true?

• A. Destination marginal only
• B. Alternate marginal only
• C. Destination and alternate are both marginal
• D. Neither is marginal

Answer: (C)

The situation tests how flight planning handles backups when weather threatens landing options. A second alternate is required only when both the destination and the first alternate are forecast to be marginal at the estimated time of arrival. “Marginal” means the weather is at or near the minimums for a safe approach and landing, so neither site is reliably usable. If the destination is marginal but the first alternate looks like it will meet minimums, you still have a workable backup with one alternate. If only the first alternate is marginal but the destination is forecast to be above minimums, you don’t yet need a second alternate. When both are marginal, there’s a real risk that neither will be usable, so you must designate a second alternate to ensure there’s another viable option.