In the event of lost communications, FAR 91.185 allows pilots to divert to a nearby airport if they encounter VMC conditions en route to their destination. But what if IMC conditions persist? Are they legally allowed to divert to another airport, which is not designated as the alternate airport in the flight plan, and shoot an approach to land? Doesn't that conflict with the regulation requiring pilots to follow "last assigned, last vectored, EFC route, route in the flight plan" in order?

I ask this question because I came across this phrase in my study material called Everything Explained (p.82): "Do not continue on to your destination if there is a suitable airport for you to land at, unless you're just minutes from your original destination."

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    $\begingroup$ A relevant column just appeared in Air Facts 'What To Do When The Panel Goes Dark' where they talk about using all the resources available to you—in and out of the cockpit. airfactsjournal.com/2017/06/panel-goes-dark $\endgroup$
    – JScarry
    Jul 3, 2017 at 18:52

3 Answers 3


AIM 6−4−1. Two-way Radio Communications Failure

a. It is virtually impossible to provide regulations and procedures applicable to all possible situations associated with two-way radio communications failure. During two-way radio communications failure, when confronted by a situation not covered in the regulation, pilots are expected to exercise good judgment in whatever action they elect to take. Should the situation so dictate they should not be reluctant to use the emergency action contained in 14 CFR Section 91.3(b).

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    $\begingroup$ That's it. If I lost all comms & datalink said both mega airport A (destination) and mega airport B (alternate) were near mins (read, congested, possible holding, maybe below mins whenI arrive), but medium-size airport C is well above mins and nearby, I'd feel good about diverting there. Probably try to pass intentions via that datalink if possible -- works better w internet/ACARS than with ADSB, obviously. Might try cellphone to FSS once low enough to get signal. $\endgroup$
    – Ralph J
    Jul 1, 2017 at 21:55
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    $\begingroup$ The whole point of setting the regs regarding lost com is to enable ATC to anticipate the pilot's course of action in that situation, isn't it? But if a pilot diverts to an airport that's not in the flight plan, would that "surprise" ATCs? $\endgroup$ Jul 2, 2017 at 6:21
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    $\begingroup$ @lemonincider In the modern ATC system you are most likely being tracked by ATC on radar so ATC can figure out what you are going to do. If you are 1/2 hour into a 4 hour flight and pass near a Class E or D airport with an approach, good sense dictates that you land for you own safety and the safety of others. Maybe what cased the comm failure is only the beginning of your problems. If you have comm failure, how likely is it that you also nav failure? Call clearance delivery 888-766-8267 and get a phone number for the ARTCC in your area and communicate by phone—not in the regs. $\endgroup$
    – JScarry
    Jul 2, 2017 at 14:09

Short answer: you're expected to follow the rules you mentioned unless it's an emergency.

The regulations are in 91.185 and they say (among other things):

Unless otherwise authorized by ATC, each pilot who has two-way radio communications failure when operating under IFR shall comply with the rules of this section.
If the failure occurs in IFR conditions, or if paragraph (b) of this section cannot be complied with [i.e. the aircraft doesn't enter VMC], each pilot shall continue the flight according to the following: [route, altitude, clearance limit rules]

As written, that seems clear: if you aren't in VMC and don't enter VMC, you "shall" continue your flight according to the usual rules. The AIM 6-4-1(c) says the same thing:

In the event of two-way radio communications failure, ATC service will be provided on the basis that the pilot is operating in accordance with 14 CFR Section 91.185. A pilot experiencing two-way communications failure should (unless emergency authority is exercised) comply with 14 CFR Section 91.185

The whole point of 91.185 is that you don't want to fly around literally blind in IMC with no way to know what other aircraft are out there. And especially in busy airspace, ATC and other pilots certainly don't want an aircraft they can't see behaving unpredictably. If the comms failure also took out your transponder, for example, then ATC could only track you on primary radar, which is quite limited.

Having said that, the AIM is clear that if the PIC decides that the situation is an emergency, then he can do whatever seems best. Comms failure by itself isn't an emergency (see the AIM 6-4-1(b)), but every situation is different and if other equipment fails or you have other safety issues to deal with then diverting might be the best decision. There are just too many possible scenarios to have a strict yes/no rule.


I agree with all answers given, but will add this: If IMC and deviating from Asssigned, Vectored, Expected or Filed, don't just squawk 7600, roll it to 7700 to get their attention and let them know you maybe aren't going to be as predictable as they might think...

Also, I was always taught to broadcast intentions in the blind just in case they can hear you, but you can't hear them. You may not fully understand the exact failure mode causing you to be lost comm. I once experienced an ICS/ headset failure where I couldn't hear a thing, but the controllers and my crew could hear me transmitting just fine.


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