What are the lost communications route rules under 14 CFR 91.185?

Under 14 CFR 91.185, if you lose two-way radio contact in IFR conditions, you must fly the route assigned by ATC, then the route you were told to expect, and if neither applies, the route filed in your flight plan — in that priority order. This ensures controllers can predict your position and sequence you for an approach. Memorizing the acronym AVE F (Assigned, Vectored/Expected, Filed) is a common study technique for the Instrument Rating Airplane Airman Certification Standards.

What altitude should I fly if I lose radio contact on an IFR flight?

14 CFR 91.185 requires you to fly the highest of three altitudes for each route segment: the altitude assigned by ATC, the altitude you were told to expect, or the minimum IFR altitude (MEA, MOCA, or other applicable minimum) for that segment. The rule uses the word 'highest' to ensure terrain and obstacle clearance is never compromised. This three-way comparison — often remembered as 'MEA' standing for Maximum of Expected, Assigned, and applicable Minimum — is a tested concept on the FAA Instrument Rating Knowledge Test.

What's the difference between the 'expected' and 'assigned' altitude in lost comm procedures?

The 'assigned' altitude is the specific altitude ATC has cleared you to maintain at the time communication is lost, while the 'expected' altitude is one ATC has told you to anticipate receiving at a future fix or time — for example, 'expect 8,000 at ALPHA.' If you were never given an expected altitude, that element simply drops out of your comparison and you use whichever of the remaining two altitudes is highest. The Instrument Flying Handbook emphasizes that the 'expect' clearance exists partly so pilots have actionable altitude guidance in exactly this kind of lost-comms scenario.

IFR Lost Communications Route and Altitude Rules

Losing radio communication in instrument meteorological conditions (IMC) is one of the most serious emergencies an IFR pilot can face. Without the ability to receive clearances, traffic advisories, or approach instructions, you must become your own controller — following a rigid, pre-published ruleset so that ATC can predict your every move and keep traffic separated from you. The governing regulation is 14 CFR 91.185, commonly called the "lost comms" rule, and every instrument-rated pilot is expected to know it as instinctively as a traffic pattern.

This article breaks down each decision — what route to fly, what altitude to maintain, and how to execute an approach — so that even under the stress of a genuine emergency you can recall the logic rather than just memorize isolated facts. The FAA knowledge test probes this topic from multiple angles, so understanding the why behind each rule is just as important as knowing the specific answers.

Confirming a Communication Failure

Before declaring lost comms, the Instrument Flying Handbook (FAA-H-8083-15) and the AIM both emphasize confirming that the failure is real. Check the obvious: is the volume turned up? Is the correct frequency tuned? Is the squelch set properly? Try your second radio, and try transmitting blind — "ATC, [callsign] is declaring lost communications, proceeding per 91.185" — because your transmitter may still be functional even if your receiver has failed. Squawk 7600 immediately on your transponder. This code alerts ATC to a two-way radio failure and triggers lost-comms procedures on their end, including clearing airspace along your expected route.

If you are still in VMC when the failure occurs, 14 CFR 91.185(b) instructs you to continue in VMC, land as soon as practicable, and notify ATC of your landing as soon as possible. The remainder of the regulation — and the bulk of the knowledge test questions — addresses the scenario where you are already in IMC or you encounter IMC after the failure.

The Route to Fly

When you lose comms in IMC, 14 CFR 91.185(c)(1) prescribes which route you must fly. The rule is structured as an ordered hierarchy, commonly remembered by the acronym AVE F (or the phrase "Assigned, Vectored, Expected, Filed"). You fly whichever of the following applies first:

A — Assigned: The route ATC last assigned in your clearance. If you were told "fly direct KAPPA, then as filed," that assignment governs.
V — Vectored: If you were being radar-vectored when comms failed, fly the direct course from your present position to the fix, route, or airway to which you were being vectored.
E — Expected: The route ATC told you to expect in a further clearance. For example, if the controller said "expect direct KEENO after GRUBBS," and you've passed GRUBBS without a new clearance, you fly direct KEENO.
F — Filed: If none of the above applies, fly the route you originally filed in your IFR flight plan.

The logic here is elegant: ATC already knows your filed route, and they know what they assigned or told you to expect. By following this hierarchy, your actual path will almost always match ATC's prediction, allowing them to protect your airspace proactively rather than reactively.

A nuance worth noting: "assigned" refers to the most recent clearance, not the original. If ATC re-cleared you direct to a fix 20 minutes into your flight, that new assignment supersedes the original routing. Always fly the last assigned route, not what you filed hours earlier.

The Altitude to Fly

14 CFR 91.185(c)(2) governs altitude. Again, you fly the highest of three values:

A — Assigned: The last altitude ATC actually cleared you to fly.
M — MEA: The Minimum Enroute Altitude for the route segment you are on or about to enter. MEAs guarantee both obstacle clearance and navigation signal reception.
E — Expected: Any altitude ATC told you to expect. If a controller said "expect 9,000 in 10 miles" and you never received that clearance before comms failed, you climb to 9,000 when you reach that point.

The reason you fly the highest of these values — rather than simply the assigned altitude — is safety. A different MEA segment may require more altitude for terrain clearance. An expected altitude was communicated for a reason. Defaulting to the highest keeps you clear of obstacles and other traffic that ATC may have sequenced below you. This "highest" rule is one of the most commonly tested and most commonly missed points on the instrument knowledge exam.

A practical example: You are assigned 8,000 feet, the current MEA is 7,000 feet, and ATC told you to expect 10,000 feet. You fly 10,000 feet — the highest of the three — until you reach a point where a different rule would apply or you begin descent for your approach.

When to Begin Descent and the Approach

14 CFR 91.185(c)(3) addresses the timing of your approach. You may begin descent from your enroute altitude and execute an approach at your destination at the earliest of the following times:

Your EFC (Expect Further Clearance) time, if one was issued. ATC assigns EFC times precisely so that if you lose comms, they know when to expect you to begin acting on that clearance.
Your ETA computed from your flight plan — specifically, the estimated time of arrival as shown in your filed flight plan or as amended en route.
Upon arriving over the destination fix or airport.

The standard practice is to fly to the destination airport's IAF (Initial Approach Fix), execute the full published instrument approach procedure, and land. ATC will have already cleared the airspace around the airport based on your expected arrival. They watch your transponder, time your arrival, and will hold other traffic accordingly. If the airport has a control tower, watch for light gun signals after breaking out of the clouds — the tower may use light signals to authorize your landing.

Choosing the Approach

The regulation does not specify which approach to fly, but the AIM and the Instrument Flying Handbook provide practical guidance. Fly the approach to the runway most likely in use based on winds and any NOTAMs you had before losing comms. If ATC previously told you to expect a specific approach, fly that one. The goal is to be predictable. Controllers will attempt to sequence you for the most logical approach and will protect that runway environment.

Fly the complete published procedure: the full initial approach segment, intermediate segment, and final approach. Do not skip segments or improvise shortcuts. The published procedure is what ATC has been trained to anticipate.

Key Numbers and Rules

Squawk 7600 immediately upon confirming two-way radio failure.
Route hierarchy: AVE F — Assigned, Vectored, Expected, Filed (fly whichever applies first).
Altitude: highest of Assigned, MEA, or Expected — never fly lower than the MEA regardless of your assigned altitude.
Begin approach at the earliest of: EFC time, filed ETA, or arrival over the destination.
In VMC at time of failure: continue VFR, land as soon as practicable (91.185(b)).
ATC will clear airspace along your expected route once 7600 is squawked; be predictable.

Memory Aid

For the route, use AVE F: Assigned, Vectored, Expected, Filed. Think of "AVE F" like "Avenue F" — the street you drive home on every day, because it's your default path.

For the altitude, use AME: Assigned, MEA, Expected — and remember to fly the highest of the three. A common memory hook: "AME for altitude — fly the AMEst (highest) you can justify."

Common Test Traps

"Highest" vs. "assigned" for altitude. The exam may present a scenario where the assigned altitude is lower than the MEA or expected altitude, expecting you to say you'll stay at the assigned altitude. The correct answer is always the highest of the three applicable values.
Confusing route priority order. A question may ask what you do when being radar-vectored — you fly direct to the fix to which you were being vectored, not your originally filed route and not some arbitrary heading. Vectored comes before Expected and Filed.
VMC vs. IMC distinction. If the failure occurs in VMC, the rule is simply to land as soon as practicable. Many students apply the full 91.185(c) IMC rules to a VMC failure scenario — that's incorrect.
EFC vs. ETA for begin-descent timing. Some exam scenarios omit an EFC time; you must then use your filed ETA. Others give both — in that case, begin descent at the earliest of the applicable times, which is usually the EFC if one was issued before comms failed.
Forgetting to squawk 7600. A question may list several correct actions and ask which is NOT required or is wrong. Failing to squawk 7600 would itself be the wrong action; always squawk 7600 first.

Mastering the logic of 14 CFR 91.185 is not just about passing your instrument knowledge test — it is a genuine life-safety skill. In a real lost-comms scenario, the controlled, methodical execution of these rules is what separates a routine landing from a potential mid-air conflict. Study the rule until you can apply it fluently under pressure, and brief your lost-comms plan before every IFR departure so it becomes second nature.