IFR: Alternate airport requirements

This regulation sets fuel requirements for Part 135 IFR operations and when an alternate airport must be filed.

The basic rule: You must carry enough fuel to fly to your destination, then to an alternate airport, plus 45 minutes reserve (30 minutes for helicopters).

The exception: You don't need an alternate airport—and therefore don't need fuel to reach one—if your destination has a published instrument approach and the weather forecast shows, for one hour before and after your ETA:

• Ceiling at least 1,500 feet above the lowest circling MDA (or if no circling approach exists, 1,500 feet above the lowest minimum or 2,000 feet above the airport, whichever is higher)
• Visibility at least 3 miles, or 2 miles more than the lowest approach minimum, whichever is greater

If these conditions aren't met, you must file an alternate and carry fuel to reach it plus the required reserve. This ensures you have options if your destination becomes unavailable.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*