When I look up Torrance Zamperini (KTOA) alternate minimums, it states, "NA when control tower closed, except for operators with approved weather reporting services."

My main questions are:

  1. Can Part 91 pilots file this airport as an alternate when the control tower is closed?
  2. Do the "operators" restrictions apply to Part 91 pilots?
  3. What is an "approved weather reporting service"?

While we are on the topic, what exactly does the word "appropriate" refer to in the text below? FAR 91.169(c) seems to indicate that almost any source of weather information is acceptable (emphasis mine):

IFR alternate airport weather minima. Unless otherwise authorized by the Administrator, no person may include an alternate airport in an IFR flight plan unless appropriate weather reports or weather forecasts, or a combination of them, indicated that, at the estimated time of arrival at the alternate airport, the ceiling and visibility at the airport will be at or above the following weather minima:

  • 1
    $\begingroup$ welcome to aviation.se. I am afraid that these are quite a lot of questions, it could be better if you could split them in different posts, because as much as they might be related, the answers might be not. $\endgroup$
    – Federico
    Apr 18, 2017 at 7:24
  • $\begingroup$ Just a guess, but the only ones who would have operational specifications with approved weather reporting services would be scheduled airlines or Part 135 operators. If the tower is closed, they would presumably have trained personnel to report the weather. $\endgroup$
    – JScarry
    Apr 18, 2017 at 15:01
  • $\begingroup$ I answered your main question, but like JScarry said, the second question about 91.169 should be broken out into its own distinct question. $\endgroup$
    – Jimmy
    Apr 18, 2017 at 17:27

2 Answers 2


First, within the context of the question, the term "operator" in the Alternate Mins section refers to a person or company that has an operating certificate. Not just Joe the Pilot who is "operating" an aircraft. So, a "Part 91 pilot" (taken from the context to mean: "pilot flying for pleasure or personal business") cannot file this airport as an alternate when the tower is closed.

Second, the term "approved weather source": In the FARs, various Parts apply to various operators (121, 125, 135). They each have similar verbiage about approved weather reporting services. For example, Part 121.101 (for domestic and flag operations) says the following (paraphrased):

No certificate holder may use any weather report to control flight unless it was prepared by the U.S. National Weather Service or a source approved by the U.S. National Weather Service. Each certificate holder shall use an approved system for obtaining forecasts and reports on each route to be flown and at each airport to be used.

You can see this related question: What sources of weather are approved by the U.S. National Weather Service? for more information.

BUT... the important point from that FAR Part 121 quote is the second sentence. ALL operators must have Operational Specification (OpSpecs) approved by the FAA before they can operate. One of the items within the OpSpecs will specifically address how and from where these weather reports and forecasts will be obtained.

So, this is the bottom line answer to the question: only "operators" can use this airport as a filed alternate when the tower is closed, since that operator will have their own "weather source" that is approved by the FAA and listed in that operator's OpSpecs.

  • $\begingroup$ Theory as to why this is so: instead of having automatic weather (ASOS/AWOS), TOA's ATIS and weather reports are made up by a weather reporter in the tower -- without that weather reporter in the tower, there's nobody there to tell folks what the conditions are, and having to do a "look-see" basis for the approach to your alternate is something the FAA doesn't want you doing, so...you can't declare it as your IFR alternate. No great loss though, because it's still usable for an actual divert, and there are plenty of other choices for a FP alternate in the area (KLGB or KONT would be mine) $\endgroup$ Apr 18, 2017 at 22:24
  • $\begingroup$ I think you may have referred to this, but some operators employ their own meteorologists and would—I presume—have approved weather sources to include their own in-house sources. $\endgroup$
    – J Walters
    Apr 19, 2017 at 20:39

Disclaimer: I did not reference the plates.

Operator would include a Part 91 flight. Approved Wx service is normally ATC, FSS, NWS or a trained observer (which I understand to include pilots).

As for what appropriate means...

I like to interpret things colored by asking myself, "What would the accident review board say?"

In light of that I would consider appropriate to mean that there are METARs and nearby TAFs. While it appears to be general practice to use a nearby airport with reporting services, it is not clear that is a good practice. Especially during frontal passage Wx at two nearby airports can be radically different.

So in conclusion, rely on METARs, TAFs, perhaps even PIREPs, but not the Channel 5 news.

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    $\begingroup$ Just for clarification, "operator" does not refer to the pilot, nor is it applicable to Part 91 flights. It only refers to a company with an operating certificate. Also, "approved wx service" means a plan written by the operator, and signed off on by the FAA. $\endgroup$
    – Jimmy
    Apr 19, 2017 at 2:32
  • $\begingroup$ For part 91, the operator may be a pilot, or as an example, the FAA considers it to be a corporate flight department. $\endgroup$
    – mongo
    Apr 19, 2017 at 21:05
  • $\begingroup$ The context of this question is about what is printed in the US Terminal Procedures Publication in reference to Alternate Minimums (Section M). Within that context, an "operator" is only an entity that has been issued an "operating" certificate under the guidelines of Part 119. This is not applicable to anyone who may be "operating" under Part 91, including any commercial activities authorized under Part 91. $\endgroup$
    – Jimmy
    Apr 19, 2017 at 22:02

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