When do you need to file an alternate under IFR?

One of the most amazing accomplishments any pilot can achieve is flying inside the clouds. Being an IFR-rated pilot is a fantastic opportunity for your career, but that comes with significant responsibilities. When will an alternate be needed for an IFR flight.? How to pick an alternate.? What regulations are involved? Is there any easy way to remember this?

First, let’s start with the basics: § 91.169 – IFR flight plan. I know the FARs use complicated phraseology, and therefore we are looking to simplify and deliver the best approach possible. § 91.169 (b) states that you ALWAYS need to file an alternate UNLESS

  • The airport has an instrument approach procedure AND
  • Appropriate weather reports OR weather forecasts, OR a combination of them, indicate the following:
    • 1 hour before to 1 hour after your ETA (at the listed destination), the ceiling will be at least 2,000′ AGL, and the visibility will be at least 3 SM. It’s called the 1-2-3 rule; this is the easiest way to remember this section.

What is considered an appropriate weather reports or weather forecasts?


Well, METAR is an observation weather report; meanwhile, the TAF is weather forecast observation of the field. For flights less than an hour, a current METAR may be used.

What if the destination has no TAF?


Although the Terminal Aerodrome Forecast (TAF) is preferable, the Graphical Area Forecast (GFA) can be used in its absence. Utilize the “Ceiling/Visibility” tab and the Zulu time sliding bar to determine weather conditions around your arrival.

It’s quiz time!

Planning your IFR alternate airport

Great job, now that you understand when an alternate is needed. Let’s talk about the conditions an airport requires to meet to qualify as an alternate. Remember, an alternate is a plan B; a professional pilot always has a plan B. As a result, you must verify different factors before even attempt to choose an airport as an alternate.

1. You have to assess the field. Use risk management, and determine the best area to pick an alternate airport.

For example, let imagine you are planning a cross country from KOPF to KJAX. There are significant areas of thunderstorms north of KJAX moving southeast. Your expected time of arrival is 23:00 Zulu. Following the regulation § 91.169 (c), you will need an alternate because of a probability of low visibility is depicted on the TAF. You are a proactive pilot and always plan ahead of time. After reviewing the forecast and current weather, you determine the best possible option will be southwest of the field due to the potentially hazardous weather that exists north moving southeast. With this type of assessment, you can eliminate and narrow it to a small list of possible alternates.

alternate jax

2. Once you identify the possible alternates, now it’s time to determine if they comply with the requirements specified in § 91.169 (c).

  • no person may include an alternate airport in an IFR flight plan unless appropriate weather reports or weather forecasts, or a combination of them, indicate that, at the estimated time of arrival (ETA) at the alternate airport, the ceiling and visibility at that airport will be at or above the following weather minima:
    • If a usable precision approach is available: 600 ft ceilings AND 2 SM of visibility.
    • If only a non-precision approach is useable: 800 ft AND 2 SM of visibility.
    • If no instrument approaches are available: Descent from the MEA and landing must be conducted under basic VFR.

3. In the real world, not all airports follow the standard minimums we just listed above here. If that’s the case, the airport has nonstandard alternate minimums. So how do you find those alternate minimums?

a) If an airport has nonstandard IFR alternate minimums information published, you will know by seeing a symbol that looks like a triangle with an ‘A’ in it on the Notes section’s approach plate.


b) To view the non-standard IFR alternate minimums information, you will need to go to the front of the TPP to the Alternate Mins Section (M1), then search for the airport, and use the notes for the desired approach.


c) If you’re using ForeFlight, you can click on the “alternate minimums” tab under “arrival procedures.” Sorted by city name, you’ll find the new weather minimums you must use to determine if an airport is eligible to file as an alternate.


d) Not all the airport are quality as an alternate, you will know by seeing an NA before the triangle with an ‘A’ in it on the Notes section’s approach plate.


RNAV approaches as alternate airport considerations

  • (AIM 1-1-18, AIM 1-1-19)
    • GPS users (without WAAS) may flight plan to use GPS based approaches at either their destination or alternate, but not at both locations
    • WAAS users without BARO-VNAV may flight plan for the use of LNAV approaches at any airport, whether the destination, alternate, or both.
    • WAAS equipped with BARO-VNAV may flight plan for LNAV/NAV or RNP 0.3 DA approaches at both, the destination and alternate. (AIM 1-1-18)

Don’t stop here, let’s keep learning!