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

Under 14 CFR 91.185, you should fly the route assigned in your last ATC clearance, or if being radar vectored, fly directly to the fix, route, or airway specified in the vector clearance. If no route was assigned, fly the route ATC has advised you to expect, or if neither applies, fly the filed route. The goal is to proceed in the most predictable manner so ATC can anticipate your position and sequence you safely.

What altitude should I fly after losing two-way radio communications in IFR conditions?

14 CFR 91.185 requires you to fly the highest of three altitudes: the last assigned altitude, the minimum IFR altitude for the route segment being flown, or the altitude ATC has advised you to expect in a further clearance. You maintain that highest altitude until you reach the destination or begin a descent for the approach. This rule ensures obstacle and terrain clearance even though ATC communication has been lost.

When should I begin my approach after losing radio communications on an IFR flight?

According to 14 CFR 91.185, you should leave the final approach fix or begin descent from the holding pattern at the expect-further-clearance (EFC) time if one was given, or if no EFC was issued, at the estimated time of arrival calculated from your filed or amended flight plan. You should then execute the approach and land as soon as practicable. Understanding this procedure is a tested concept on the FAA Instrument Rating Airplane Knowledge Test and is aligned with the FAA Instrument Rating Airman Certification Standards.

Lost Communications Procedures Enroute (FAR 91.185)

Losing radio contact in instrument meteorological conditions (IMC) is one of the most stressful events an IFR pilot can face. Without the ability to receive ATC clearances, how do you know where to go, how high to fly, and when to start an approach? The answer lies in 14 CFR Part 91.185, a regulation that gives you a complete, deterministic set of rules to follow so that both you and ATC can predict your behavior — making a safe outcome far more likely.

The goal of 91.185 is elegant: if both sides of the radio equation know exactly what the pilot will do, ATC can sequence traffic around the lost-comms aircraft and have the airport ready. As a student, you need to understand these rules deeply — not just memorize them — because the FAA knowledge test asks about them in tricky, scenario-based ways.

First: Try to Restore Communications

Before diving into routing and altitude rules, the regulation — and common sense — demands you attempt to regain communication. Try all of your radios. Transmit on the last assigned frequency, then on 121.5 MHz (the universal emergency frequency monitored by virtually all ATC facilities). Try your transponder: squawk 7600, which alerts ATC to a radio communications failure. Switch your audio panel and check circuit breakers. Attempt to receive a clearance through an FSS or even a company frequency. If you can receive but not transmit, ATC may relay instructions through another aircraft or ask you to ident to confirm reception. Only after exhausting these options should you treat the situation as a true lost-comms event under 91.185.

VFR vs. IMC: The First Decision Point

The regulation draws a critical fork in the road based on the weather conditions you encounter. If the weather along your route and at your destination is VMC (Visual Meteorological Conditions), you must continue VFR and land as soon as practicable. The logic is straightforward — in visual conditions you can see and avoid traffic, so there is no need to continue operating as an IFR aircraft clogging up the ATC system. Land at the nearest suitable airport where it is safe to do so.

If the weather is IMC, or if descending to VFR would put you into IMC, the full lost-communications procedure under 91.185 kicks in. You remain on your IFR flight plan and follow the specific route and altitude rules below.

Route to Fly

When operating in IMC with no radio contact, 91.185 tells you which route to fly in priority order. You must fly whichever of the following applies first:

Assigned: Fly the route ATC last assigned you. If ATC gave you a specific routing — even a radar vector — that is your assigned route.
Vectored: If you were being radar-vectored when comms failed, proceed direct to the fix, route, or airway to which you were being vectored.
Expected: Fly the route ATC told you to expect in a further clearance. For example, if the controller said "Expect direct BOSOX after CEDAR," that constitutes an expected routing.
Filed: As a last resort, fly the route you filed in your flight plan.

The memory device most instructors use for this sequence is AVE F — Assigned, Vectored, Expected, Filed. This priority order makes intuitive sense: the most recent information ATC gave you is the most useful, because it reflects their latest traffic management picture.

Memory Aid

AVE F — for lost-comms route selection:

A — Assigned route (last ATC clearance)
V — Vectored (direct to the fix being vectored toward)
E — Expected (route ATC told you to expect)
F — Filed (your original filed flight plan route)

Work through AVE F from top to bottom and use the first one that applies. In most practical scenarios, you will have an assigned routing, so "A" governs.

Altitude to Fly

Altitude selection under lost comms is governed by the concept of flying the highest of three possible altitudes for each portion of the route. The regulation specifies:

Assigned: The altitude or flight level ATC last assigned.
Minimum IFR Altitude (MIA): The applicable minimum IFR altitude for the route segment — typically the Minimum Enroute Altitude (MEA) or Minimum Obstruction Clearance Altitude (MOCA) published on enroute charts.
Expected: The altitude ATC told you to expect. For instance, if the controller said "Expect 9,000 in 10 minutes," you should climb to 9,000 at that point even though you never received the formal clearance.

You fly the highest of these three. The initials here are also convenient: MEA can remind you — but the formal set is Assigned, Minimum IFR, Expected. Why the highest? Because altitude is your safety margin. Flying higher than strictly necessary keeps you clear of terrain and other IFR traffic at lower altitudes, and ATC can always work around a higher aircraft more safely than one that has descended into the traffic stream without a clearance.

A critical subtlety involves the expected altitude: if ATC said "Expect Flight Level 210 in 30 miles" and you lose comms 10 miles later, you should climb to FL210 when you reach that point. This is precisely why controllers issue "expect" instructions — so pilots have the information to handle exactly this scenario. As a student, remember that the expected altitude phraseology is not just courtesy; it has regulatory weight during lost comms.

When to Leave the Clearance Limit and Begin the Approach

Knowing when to descend and start an approach is the third piece of the puzzle, and arguably the most operationally complex. The regulation distinguishes between two situations:

If the Clearance Limit Is a Fix from Which an Approach Begins

In this case, you begin your descent and approach as close as possible to the Expected Further Clearance (EFC) time if one was issued. If no EFC was issued, you begin the approach at the estimated time of arrival (ETA) calculated from your filed or amended flight plan. The idea is simple: ATC is counting on you to start the approach at a predictable moment so they can protect the airspace.

If the Clearance Limit Is NOT a Fix from Which an Approach Begins

Fly to the clearance limit and hold. Then leave the holding fix at the EFC time, or if none was given, at your ETA. Proceed to an approach fix and begin the approach. Do not simply descend below the clearance limit altitude without following this sequence — ATC may have traffic that you cannot see on the approach path.

Why These Rules Matter in Practice

The beauty of 91.185 is that it creates a shared mental model. ATC radar controllers know this regulation, and as soon as they see a 7600 squawk, they begin predicting where the aircraft will go based on these exact rules. They will typically coordinate with the destination airport and other facilities to have emergency equipment standing by if needed. They will also clear the approach path and hold other traffic. For this system to work, you — the pilot — must follow the regulation precisely. Deviating from AVE F routing or flying a lower altitude than the highest of the three choices disrupts the entire protective bubble ATC tries to build around you.

From a practical standpoint, this regulation also underscores the value of full pre-flight planning. Know your filed route cold. Brief every "expect" clearance carefully and write it down, because that information becomes operationally binding if you lose comms. Confirm your EFC time any time you are placed in a hold.

Key Numbers and Rules

Squawk 7600 for radio failure (NORDO); squawk 7700 for general emergency; squawk 7500 for hijacking.
In VMC: continue VFR and land as soon as practicable — do NOT continue IFR.
Route priority: Assigned → Vectored → Expected → Filed (AVE F).
Altitude: fly the highest of Assigned, Minimum IFR, or Expected.
Begin approach at EFC time, or if none given, at your filed/amended ETA.
If not at an approach fix, hold at the clearance limit until EFC or ETA, then proceed.
121.5 MHz is the universal emergency frequency — monitor and transmit on it during troubleshooting.

Common Test Traps

"Lowest" vs. "highest" altitude: Students sometimes confuse the altitude rule. The regulation says fly the HIGHEST of the three altitudes, not the lowest. The FAA test frequently presents distractors using "lowest."
VMC escape hatch: Many students forget that if you can maintain VFR, you MUST do so and land. The full lost-comms procedure only applies in IMC or when entering IMC. A question showing VFR weather should lead you to answer "continue VFR and land as soon as practicable."
"Expected" altitude has real weight: Some students think the expected altitude instruction is just advisory. It is not — under lost comms, you climb to the expected altitude at the appropriate time.
Vectored route vs. assigned route: If you were being radar-vectored, your "assigned" route may just be a heading. In that case, the vectored provision (V in AVE F) tells you to proceed direct to the fix you were being vectored toward — not to keep flying that heading indefinitely.
EFC vs. ETA timing: If an EFC was issued, use it. If not, use your ETA from the flight plan. The test will often give you a scenario where an EFC exists but students default to ETA — or vice versa. Read the scenario carefully.