What are lost communications procedures for manned aircraft and why does a remote pilot need to know them?

Lost communications (lost-comms) procedures are the standardized steps a manned aircraft pilot follows when two-way radio contact with ATC fails, including squawking transponder code 7600 and following the route and altitude rules outlined in 14 CFR 91.185. Remote pilots need to understand these procedures because a manned aircraft operating under lost-comms rules may enter or transit airspace near UAS operations in a predictable but potentially unexpected way. Recognizing transponder code 7600 and understanding the manned aircraft's likely behavior helps a remote pilot make smart yield decisions to maintain safety of flight. This topic is tested on the FAA Unmanned Aircraft General – Small Unmanned Aircraft Systems Knowledge Test.

What does squawking 7600 mean and how should a remote pilot respond if they see an aircraft behaving unusually near their operation?

Squawking 7600 means a manned aircraft pilot has set their transponder to the universal lost-communications code, signaling to ATC and other traffic that two-way radio contact has been lost. Under 14 CFR 91.185, the pilot will generally continue on the last assigned route and altitude, follow any previously issued clearance, and ultimately attempt to land at the destination in accordance with published procedures. A remote pilot observing an aircraft behaving in a pattern consistent with lost-comms—such as following a published approach path without radio interaction—should immediately land or maneuver the UAS clear of the aircraft's likely flight path. The remote pilot in command always retains the responsibility under 14 CFR Part 107 to see and avoid manned aircraft and yield the right-of-way.

How do Part 107 rules interact with lost communications procedures when a remote pilot is operating near controlled airspace?

Under 14 CFR Part 107, remote pilots must receive an airspace authorization before operating in controlled airspace, but a lost-comms situation involving a manned aircraft can quickly change the traffic picture even in approved areas. Because a manned aircraft under lost-comms will not be actively communicating position information, the remote pilot cannot rely on radio calls or ATC advisories for traffic awareness and must depend entirely on visual scanning. The FAA emphasizes in the Aeronautical Information Manual and the PHAK that right-of-way rules always favor manned aircraft, so the remote pilot must be prepared to descend and land immediately if a conflict appears likely. Maintaining situational awareness of published instrument approaches and VFR traffic patterns near the operation site is a key risk-mitigation strategy covered in remote pilot training materials.

Lost Communications Procedures Relevant to Remote Pilot Operations

Most small unmanned aircraft systems (sUAS) under Part 107 do not carry radios capable of two-way ATC communication. Yet lost communications procedures are a tested topic on the FAA Part 107 Aeronautical Knowledge Test for a very practical reason: the airspace remote pilots fly in is shared with manned aircraft, and manned aircraft experiencing radio failure follow specific, predictable procedures that every pilot—remote or otherwise—must understand. Knowing how those procedures work helps a remote pilot make smarter decisions about when and where to operate, especially near airports and controlled airspace.

This article explains what lost communications (often called "NORDO," short for no radio) means in the context of manned aviation, how ATC handles a radio-failure aircraft, what signals and procedures apply, and how all of this connects directly to the remote pilot's responsibilities under 14 CFR Part 107 and the Aeronautical Information Manual (AIM).

What Lost Communications Means in Manned Aviation

A manned aircraft is considered to have lost communications (lost comms) when the pilot can neither transmit nor receive on the assigned frequency—or when the aircraft has no functioning radio at all. This situation creates a significant hazard in controlled airspace because ATC can no longer sequence or separate that aircraft from others in the normal way. The FAA has developed a standardized set of procedures—published in the AIM and in 14 CFR 91.185—to make the behavior of a NORDO aircraft predictable, so controllers and other pilots can anticipate what it will do next.

Under 14 CFR 91.185, if a pilot loses two-way radio communication in VFR conditions, the pilot must continue VFR and land as soon as practicable. In IFR conditions, the rules are more complex: the pilot must fly specific routes (the last assigned route, the route expected, or the filed route—in that priority order) and descend at the expected or filed altitude. The key concept for the remote pilot knowledge test is that a NORDO aircraft follows rule-based, predictable behavior, not random flight. ATC counts on this so they can protect airspace and sequence the aircraft safely.

Light Gun Signals: ATC's Backup Communication Tool

When voice radio communication fails, ATC can still communicate with an aircraft using a light gun—a device at the control tower that projects a narrow, intense beam of colored light directed at a specific aircraft. The AIM describes the standard meanings of these signals, and they appear regularly on the Part 107 knowledge test. Understanding light gun signals is important for remote pilots because if they are operating near a towered airport under a waiver or authorization and any communication issue arises, or if they witness unusual tower signals, they need to interpret what is happening in the traffic environment around them.

Light Gun Signal Meanings

Steady green: Cleared to land (for aircraft in flight); cleared to cross or proceed on the runway (for aircraft on the ground).
Flashing green: Return for landing (for aircraft in flight); cleared to taxi (for aircraft on the ground).
Steady red: Give way to other aircraft and continue circling (for aircraft in flight); stop (for aircraft on the ground).
Flashing red: Airport unsafe—do not land (for aircraft in flight); taxi clear of the runway in use (for aircraft on the ground).
Flashing white: Return to starting point on airport (for aircraft on the ground only).
Alternating red and green: Exercise extreme caution (for both aircraft in flight and on the ground).

A pilot acknowledging a light gun signal during the day rocks the aircraft's wings; at night, the pilot flashes the landing lights or navigation lights on and off. Remote pilots will not personally receive light gun signals during sUAS operations, but they are expected to know these signals for the knowledge test and for situational awareness when operating near towered airports.

How Squawk Codes Factor In

Another lost-comms tool involves the aircraft's transponder. If a pilot loses radio communication, they should squawk transponder code 7600. This code immediately alerts ATC radar displays that the aircraft has lost communication. Knowing the emergency and special squawk codes is a Part 107 knowledge test requirement because remote pilots need broad aeronautical knowledge to safely share airspace. The three most important codes are:

7500: Hijacking or unlawful interference.
7600: Lost communications (radio failure).
7700: Emergency (general).

A helpful memory device: 75—taken alive, 76—lost in the sticks, 77—going to heaven is a widely known student mnemonic. When ATC sees 7600, they will attempt to reestablish contact on other frequencies and may use light gun signals as a backup.

Why This Matters for Remote Pilots Specifically

Under 14 CFR Part 107, a remote pilot in command (RPIC) is responsible for the safe operation of the sUAS and must yield the right of way to all manned aircraft (§107.37). A manned aircraft experiencing lost communications is still flying its predictable NORDO route, but it may not be where other pilots expect it—and its crew is already stressed. This is precisely why remote pilots must:

Avoid flying near airports without proper authorization (LAANC or a Part 107 waiver), where a NORDO aircraft returning to land would be concentrated.
Maintain visual contact with the sUAS and scan the surrounding airspace continuously, because a NORDO aircraft will not be communicating its position on any frequency the remote pilot could monitor.
Understand traffic pattern procedures around airports, because a NORDO aircraft entering Class D airspace will fly the standard traffic pattern and look for light gun signals from the tower. Knowing the pattern means the remote pilot can predict where that aircraft will be.
File any required notifications with ATC when operating near airports and monitor the appropriate CTAF or tower frequency, even though Part 107 does not require sUAS to carry radios. Monitoring provides critical situational awareness.

Part 107 and Radio Requirements

Part 107 does not require an sUAS to be equipped with a radio or transponder, and remote pilots are not required to communicate with ATC during normal operations—unless they are operating under a specific authorization that includes communication requirements. However, if a remote pilot is operating in Class B, C, or D airspace, or within the lateral limits of a surface area, they must have received prior authorization from ATC (§107.41). Some authorizations granted through LAANC or DroneZone may carry specific conditions, including monitoring a particular frequency. Always read your authorization carefully.

When a remote pilot voluntarily monitors the tower frequency near a towered airport, they gain the ability to hear if ATC is dealing with a NORDO inbound aircraft, which may prompt the remote pilot to immediately land or move out of the area as a precaution.

Key Numbers and Rules

14 CFR 91.185: Governs manned aircraft lost communications procedures (VFR: land as soon as practicable; IFR: follow route/altitude rules).
Squawk 7600: Transponder code for lost communications in manned aircraft.
14 CFR 107.37: Remote pilots must yield right of way to all manned aircraft at all times.
14 CFR 107.41: Operations in controlled airspace require ATC authorization.
Light gun signals: Six signals—steady green, flashing green, steady red, flashing red, flashing white, and alternating red/green—with different meanings for aircraft in flight versus on the ground.
Maximum altitude under Part 107: 400 feet AGL (or within 400 feet of a structure), well below most manned aircraft traffic, which reduces but does not eliminate lost-comms conflict risk.

Common Test Traps

Confusing light gun meanings for airborne vs. ground: The FAA test often asks what a specific signal means for an aircraft already in flight versus one on the ground. Steady green means cleared to land in flight but cleared to cross a runway on the ground—these are different answers.
Mixing up squawk codes: 7500, 7600, and 7700 are frequently tested as a set, and the test may give you a scenario and ask which code applies. Do not confuse 7600 (lost comms) with 7700 (general emergency).
Assuming Part 107 exempts remote pilots from needing aeronautical knowledge: The test explicitly covers VFR lost-comms procedures under 91.185 because remote pilots share airspace with manned aircraft and need this situational awareness.
Thinking lost comms only applies to IFR operations: 14 CFR 91.185 covers both VFR and IFR scenarios. VFR lost comms is simpler (land as soon as practicable) but still a tested procedure.
Overlooking the right-of-way rule: No matter what a manned aircraft is doing—including flying a non-standard path because of radio failure—the remote pilot must always yield. Never assume a manned aircraft will deviate for your sUAS.

Understanding lost communications procedures gives a remote pilot a richer picture of how manned aviation operates and what to expect in the shared airspace environment. This knowledge isn't just about passing a test—it directly informs the judgment calls that keep both your drone and manned aircraft safe every time you fly.