What route should I fly if I lose radio communication while flying IFR?

Under 14 CFR 91.185, you should fly the route assigned in your last ATC clearance, or if being radar vectored, fly the direct route from the point of communication failure to the fix, route, or airway specified in the vector clearance. If you were cleared via a specific routing before the vector, you should proceed via that routing. The goal is to fly the most predictable path so ATC can anticipate your position and protect airspace for you.

What altitude should I maintain after losing communications in IMC under FAR 91.185?

14 CFR 91.185 requires you to fly the HIGHEST of three altitudes: the altitude assigned in your last ATC clearance, the minimum IFR altitude for the route segment being flown, or the altitude ATC has advised you to expect in a further clearance. This 'highest of' rule ensures you maintain safe terrain and obstruction clearance even without updated ATC guidance. Memorizing this as 'MEA, Assigned, Expected — whichever is highest' is a common study technique aligned with Instrument Rating Airman Certification Standards preparation.

When should I leave a clearance limit if I lose communications while holding IFR?

Under 14 CFR 91.185(c)(3), if the clearance limit is a fix from which an approach begins (which may or may not be the destination airport), you should begin descent, or descent and approach, as close as possible to the expect-further-clearance (EFC) time if one was given, or if no EFC was issued, as close as possible to your estimated time of arrival (ETA) based on your filed or amended flight plan. If the clearance limit is a fix that is not one from which an approach begins, you should leave that fix at the EFC time if one was given, or if no EFC was issued, upon arrival over the fix, and then proceed to a fix from which an approach begins, timing your descent to your calculated ETA. Following these timing rules allows ATC to sequence your arrival and keep separation from other traffic even without radio contact.

Lost Communications Procedures under IFR (FAR 91.185)

Losing two-way radio communication in instrument meteorological conditions (IMC) is one of the most stress-inducing scenarios an IFR pilot can face. Without the ability to talk to ATC, you must make a series of critical decisions about where to fly, how high to fly, and when to begin your approach — all while maintaining the safety of your flight and avoiding conflicts with other IFR traffic. Fortunately, 14 CFR 91.185 lays out a precise set of procedures that, once mastered, transform a potentially chaotic emergency into a methodical, predictable sequence of actions. Every instrument-rated pilot must know these rules not just for the knowledge test, but because ATC controllers also know them — and they will expect you to follow them if your radio goes silent.

Before diving into the rules themselves, it is worth understanding the fundamental philosophy behind them. ATC's job, in part, is to keep IFR aircraft separated. When a pilot goes "NORDO" (no radio), controllers use 91.185 as the framework to predict where that aircraft will go. As long as the pilot follows these procedures faithfully, ATC can protect the appropriate airspace and sequence the pilot for an approach. If the pilot deviates unpredictably, separation assurance collapses. So these rules are not arbitrary bureaucracy — they are the shared language that keeps lost-comm situations from becoming fatal.

First Step: VFR or IMC?

The very first question 91.185 asks is whether you can operate VFR. If you encounter a lost-comm situation and the weather allows, you are expected to continue VFR and land as soon as practicable. This is the simplest possible outcome — squawk 7600 on your transponder (which alerts ATC to your situation), and get the aircraft on the ground at the nearest suitable airport while remaining clear of clouds and meeting VFR minimums. The 7600 squawk is critical; radar facilities will see it immediately and begin coordinating airspace protection on your behalf.

The harder, more test-relevant scenario is when you are already in IMC or must enter IMC to get to an airport. In that case, the full procedures of 91.185(c) apply, broken into three distinct components: route, altitude, and leaving the clearance limit. Think of these as three separate questions you must answer in sequence.

Route: Where Do You Fly?

The route rules follow a strict priority order, and the FAA knowledge test loves to probe which route takes precedence. Use the memory device AVE F — Assigned, Vectored, Expected, Filed — to remember the hierarchy:

Assigned: Fly the route you were last assigned by ATC. If your last clearance was direct to a VOR, continue direct to that VOR.
Vectored: If you were being radar-vectored when comm was lost, fly direct to the fix, route, or airway that the vector was taking you to — in other words, reconnect with the underlying route the vector was replacing.
Expected: If ATC had told you to "expect" a certain route or clearance in a future transmission, fly that route. Controllers often issue these advisories precisely so pilots have a fallback if comm is lost.
Filed: If none of the above apply, fly the route you originally filed in your flight plan.

The order of priority matters. Do not jump to your filed route if you have an assigned route — the assigned route is always first. One common test trap is assuming that "what you filed" is always the answer; it is only the last resort.

Altitude: How High Do You Fly?

The altitude component of 91.185 is elegant because it simultaneously accounts for terrain clearance and ATC's need to predict your position. You must fly the highest of the following three altitudes for each route segment:

The last assigned altitude: Whatever ATC told you to maintain when you last spoke to them.
The minimum IFR altitude (MIA) for the route segment: This is the minimum en route altitude (MEA) or other applicable MIA for the segment you are flying. This ensures obstacle and terrain clearance even if your last assigned altitude was below the MEA for a subsequent segment.
The altitude ATC told you to expect: If a controller said "expect 8,000 in 10 miles," you should climb to 8,000 as if that clearance had been issued, because the controller may have issued that advisory specifically to protect you in a lost-comm scenario.

Note the critical word: highest. This is not an average or a choice — you take whichever of these three values is greatest. On the knowledge test, you will often see a scenario where the assigned altitude is lower than the MEA for an upcoming segment; in that case, you must climb to the MEA because it is the highest applicable value.

Practical altitude example

Suppose you were last assigned 6,000 feet, the MEA for the segment ahead is 7,000 feet, and ATC told you to expect 8,000 feet in 20 miles. Your lost-comm altitude is 8,000 feet — because that is the highest of the three. You climb to 8,000 and maintain it for that segment, then re-evaluate at each subsequent segment using the same logic.

Leaving the Clearance Limit: When Do You Descend and Shoot the Approach?

Once you reach your clearance limit, you need to know exactly when to begin your descent and execute an approach. Under 91.185(c)(3), the applicable rule depends on whether your clearance limit is a fix from which an approach begins (this may or may not be the destination airport itself), or some other fix that is not an approach fix.

If your clearance limit is a fix from which an approach begins (commonly the destination airport, but it could be an initial approach fix short of the field): Begin your descent, or descent and approach, as close to your expected further clearance (EFC) time as possible, or if no EFC was issued, as close to your estimated time of arrival (ETA) as calculated from your filed or amended flight plan. The logic is that ATC expected you at a certain time and has protected the approach environment accordingly.
If your clearance limit is a fix that is not a fix from which an approach begins (for example, a holding fix well short of the airport with no published approach starting there): Leave the clearance limit at your EFC time if one was given. If no EFC was given, leave the clearance limit upon arrival over it, then proceed to a fix from which an approach begins and commence descent or descent and approach as close as possible to your calculated ETA.

A subtle but testable point: if you arrive at a clearance-limit fix that is not a fix from which an approach begins and no EFC time was issued, you should proceed immediately upon arrival toward a fix from which an approach begins, timing your descent to that fix around your calculated ETA — not sit and hold indefinitely. This protects other traffic and allows ATC to sequence you.

Approach Selection

Once you are cleared to begin an approach (by your own internal timing under 91.185), you should fly the most suitable approach for the runway environment, weather, and your aircraft capabilities. There is no specific FAA requirement under 91.185 that mandates a particular approach type in a lost-comm situation, but the expectation is that you will execute a published instrument approach procedure to the airport named in your flight plan.

Why It Matters

The value of 91.185 goes beyond the knowledge test. Every time you receive a clearance in the real world, you should be mentally noting your assigned altitude, your expected altitude, and your filed route — because any of those could become your lifeline if your radios fail. Good IFR pilots think one step ahead: "If I lost comm right now, what route would I fly, what altitude would I hold, and when would I start down?" That mental habit costs nothing and can make all the difference.

It is also worth noting that ATC will attempt to re-establish contact with you by all available means: broadcasting on frequencies you were using, on guard frequency (121.5 MHz), through other aircraft, and via NAVAIDs. If you can receive but not transmit, try rocking your wings, keying the mic a set number of times, or using transponder functions. Some approach control facilities will instruct you to "ident" or squawk a specific code to confirm you are reading them. These two-way communication attempts do not change your obligation to follow 91.185, but every bit of information you can convey helps ATC help you.

Key Numbers and Rules

Squawk 7600 immediately upon recognizing lost comm — not 7700 (emergency) unless you also have an emergency.
Route priority: AVE F — Assigned, Vectored, Expected, Filed.
Altitude: fly the highest of last assigned, minimum IFR altitude for the segment, or expected altitude.
At a clearance limit that is a fix from which an approach begins: begin descent/approach at EFC time, or ETA if no EFC was given.
At a clearance limit that is not a fix from which an approach begins: leave the fix at EFC time, or upon arrival if no EFC, then proceed to an approach fix and time your descent to your ETA.
These rules apply only in IMC (or when descent into IMC would be required). In VMC, land as soon as practicable.

Memory aid

Use AVE F for route priority: Assigned — Vectored — Expected — Filed. For altitude, remember the phrase "Fly the highest" — last Assigned, Minimum IFR, Expected. And for timing at the clearance limit, remember "EFC or ETA" — whichever was given, honor it to the minute.

Common Test Traps

Confusing "highest" with "assigned": Many students automatically fly the last assigned altitude. Remember — if the MEA or expected altitude is higher, you must fly that higher value.
Filing as the first choice: The filed route is last in the priority order (AVE F). The knowledge test frequently offers it as an attractive first option.
Squawking 7700 instead of 7600: 7700 is a general emergency; 7600 specifically signals radio failure. Use 7600 for lost comm unless you have a concurrent emergency.
Forgetting the EFC vs. ETA distinction: If ATC gave you an EFC time, use that — do not simply use your own ETA. If no EFC was issued, then and only then do you calculate and use your ETA.
Treating the VMC option as optional: If you can maintain VFR, you must land as soon as practicable. Many students want to default to the IMC procedures because they studied them — but 91.185 requires VFR if the weather allows it.