Which FAR section governs the requirement to file an alternate for IFR operations under Part 135?

• A. 135.223
• B. 91.205
• C. 121.435
• D. 43.39

Answer: (A)

In IFR operations under Part 135, the rule that specifies when and how to file an alternate is found in 14 CFR 135.223. This regulation lays out the conditions under which an alternate aerodrome must be designated in the flight plan, what counts as an acceptable alternate, and the considerations for ensuring the aircraft can reach that alternate if landing at the destination isn’t possible. It ensures you have a viable backup option if weather or other factors prevent a landing at the destination, covering both the requirement to file and the criteria for selecting an appropriate alternate. The other cited sections address different topics—general IFR equipment requirements, Part 121 flight planning, and maintenance records—so they don’t govern the alternate-filing requirement for Part 135 IFR operations.