What happens when a drone loses its command-and-control link under FAA Part 107?

Under 14 CFR Part 107, when a small unmanned aircraft loses its command-and-control link, the remote pilot in command is responsible for ensuring the aircraft does not pose a hazard to other aircraft, people, or property on the ground. Most flight control systems allow the operator to pre-program a failsafe response — such as hovering in place, returning to the launch point, or initiating a controlled landing — that activates automatically when the link is lost. The remote pilot must understand and configure this behavior before each flight, because the FAA holds the remote pilot accountable for the aircraft's actions even during an uncontrolled loss-of-link event.

How do you configure a lost link failsafe on a drone for Part 107 operations?

Configuring a lost link failsafe typically involves using the drone manufacturer's ground station software or companion app to set the desired response — commonly return-to-home, hover, or auto-land — along with a return altitude that clears local obstacles and keeps the aircraft within the visual line of sight of the remote pilot or visual observer. The remote pilot should verify the home point is correctly set before every flight, since an incorrect home point can cause the aircraft to fly to an unintended location. Part 107 does not mandate a specific failsafe action, but the chosen setting must be consistent with the remote pilot's overall safety plan and any applicable airspace authorizations or waivers.

What's the difference between a lost link failsafe and an emergency procedure under Part 107?

A lost link failsafe is an automated, pre-programmed response built into the aircraft's flight controller that activates when communication between the remote pilot's control station and the aircraft is interrupted, requiring no real-time pilot input. An emergency procedure, as addressed in 14 CFR Part 107.21, is an action the remote pilot actively takes — deviating from regulations if necessary — to meet an immediate safety-of-flight threat such as a fly-away, battery failure, or imminent collision. Both concepts require advance planning: the remote pilot should configure the failsafe to minimize risk during a link loss and separately brief emergency procedures so that deliberate corrective actions can be taken quickly if the automated response itself is insufficient.

Lost Link Procedures and Failsafe Configuration

Every remotely piloted aircraft system (RPAS) relies on a continuous radio link between the ground control station (GCS) and the aircraft. When that link is interrupted — even briefly — the drone can no longer receive pilot commands. What happens in those critical seconds defines whether the flight ends safely on the ground or becomes an uncontrolled hazard in the National Airspace System (NAS). Under 14 CFR Part 107, the remote pilot in command (RPIC) is legally responsible for the outcome regardless of whether the aircraft was responding to inputs at the time. Understanding lost link procedures and properly configuring your aircraft's failsafe behavior is therefore not optional — it is a fundamental pre-flight obligation.

This article examines what the FAA expects of remote pilots regarding lost link events, how modern failsafe systems work at a technical level, what must be configured before flight, and the operational procedures that keep bystanders and other airspace users safe when the link goes down.

What Is a Lost Link Event?

A lost link (sometimes called a datalink failure or RC failsafe) occurs when the radio frequency (RF) connection between the transmitter/GCS and the drone is interrupted long enough for the flight controller to detect a signal loss. This can happen for many reasons: the pilot flies beyond the effective range of the control system, a physical obstruction blocks the RF path, radio-frequency interference (RFI) from nearby electronics overwhelms the receiver, or battery power in the transmitter or receiver drops too low to sustain communications.

Lost link is distinct from a GPS or navigation failure. A drone can lose its datalink while still knowing exactly where it is — or it can lose GPS while still receiving control inputs from the pilot. The two failures can also occur simultaneously, which makes pre-planned failsafe logic especially important.

The FAA's Regulatory Framework

14 CFR Part 107 does not prescribe a single mandatory failsafe behavior, but it does establish the overarching rule: the RPIC is responsible for the safe outcome of every flight. Section 107.19 states that the RPIC must ensure the drone does not pose a hazard to other aircraft, people, or property. Section 107.31 establishes that the RPIC (or a visual observer working with the RPIC) must maintain visual line of sight (VLOS) with the unmanned aircraft, and section 107.51 sets operating limitations — including visibility and cloud clearance requirements — that must be met for the flight to proceed. These rules together imply that if you can no longer see your aircraft and cannot control it, you have already violated multiple sections — which is exactly why lost link planning must happen before the motors spin up, not after the link drops.

The FAA's guidance on small UAS operations also makes clear that operators must understand their specific aircraft's behavior during a communication failure. This is an item evaluated during the Part 107 knowledge test and is a baseline expectation for a waiver under section 107.200.

How Failsafe Systems Work

Modern flight controllers allow the RPIC to program one or more automatic responses that activate when the RF link is lost for a defined period — typically one to three seconds, though this threshold is configurable on many platforms. Three standard failsafe behaviors are found across most commercial and hobbyist-grade flight systems:

Return-to-Home (RTH): The aircraft climbs to a pre-set altitude, flies back to its recorded home point (usually the takeoff location), and lands. This is the most common default behavior and is generally the safest option when flight occurs in an open area with a clear GPS fix.
Hover: The aircraft stops moving and holds its current position using GPS. This gives the pilot time to regain link or reposition to restore line of sight. It works well for short-duration link drops but can create a hazard if the link is never restored.
Land in Place: The aircraft immediately begins a vertical descent and lands at its current location. This minimizes the distance the drone travels without pilot control but can be hazardous if the drone is over people, vehicles, or water.

Some advanced platforms offer a low-battery failsafe that is separate from the link-loss failsafe, as well as a geofence failsafe that triggers if the aircraft crosses a pre-defined boundary. While these are valuable tools, the link-loss failsafe is the one most relevant to Part 107 exam content and real-world emergency planning.

Configuring Failsafe Before Flight

Proper pre-flight configuration of the failsafe is not a one-time setup task — it must be verified before each flight because conditions change. A Return-to-Home altitude that was safe at one location may be completely inadequate at a site with tall trees or obstacles. The following steps reflect best practices aligned with FAA guidance on RPIC responsibility:

Set the RTH altitude above all obstacles within the flight area. Survey the environment before flight and choose an RTH altitude that clears the tallest structure or terrain feature in every direction the aircraft might travel home. The FAA reminds operators under Part 107 that the RPIC must avoid obstacles — the failsafe must reflect local conditions, not factory defaults.
Confirm the home point has been recorded correctly. Most systems record the home point at power-on. If you power on indoors or in a magnetically noisy environment and then move to your actual launch site, the recorded home point may be wrong. Always verify the home point is set to the actual takeoff location.
Choose a failsafe behavior appropriate to the flight environment. RTH is preferable in open areas. Hover may be better in constrained urban environments where an autonomous flight home could overfly people. Land-in-place is rarely ideal but may be the best option over a controlled, unpopulated area directly beneath a persistent hover point.
Test the failsafe at low altitude before operational flights. Conduct a brief, controlled test — typically by switching the controller off for a moment at low altitude over a safe area — to confirm the aircraft responds as programmed. Never assume factory configuration is correct or unchanged.
Review the link-loss timer. The time delay before failsafe activates should be short enough to prevent uncontrolled drift but long enough to avoid triggering RTH during momentary link interruptions caused by normal RF fluctuation. Most manufacturers recommend one to three seconds.

Pilot Actions During a Lost Link Event

Even a perfectly configured failsafe does not eliminate the RPIC's responsibilities. If you experience a lost link event, the following actions are appropriate:

Attempt to re-establish the link immediately. Walk toward the last known position of the aircraft to reduce range and improve signal strength. Check for transmitter power issues and eliminate potential sources of RF interference near the GCS.
Maintain visual contact with the aircraft. If you can still see the drone, observe what the failsafe is doing and whether it appears to be behaving as programmed. Call out the aircraft's behavior to a visual observer if one is present.
Alert other people in the area. If the drone appears to be drifting or descending toward people, shout a warning. Your first priority is the safety of people on the ground.
Be prepared to declare an emergency. If the aircraft is operating near a controlled airport, contact ATC via radio or phone to alert them of an uncontrolled drone in the area. The RPIC's responsibility to avoid hazards to manned aircraft does not end because the drone is not responding to commands.
Document the event. FAA regulations and sound safety management practices both call for honest post-incident review. Note what failed, why, and what configuration changes or operational changes you will make before the next flight.

Why Lost Link Planning Matters

A drone operating without pilot command is, in regulatory terms, no different from any other uncontrolled object in the airspace. At typical small UAS operating speeds, a drone traveling for even thirty seconds without control can cover a significant horizontal distance. If that trajectory intersects a manned aircraft's approach path, a crowd, or a roadway, the consequences can be severe. The FAA has emphasized in its Part 107 rulemaking that the RPIC's accountability does not pause during a datalink failure — the expectation is that you anticipated the failure and planned for it.

From a practical standpoint, lost link events are more common than many new remote pilots expect. RF environments at many popular flying locations are cluttered with Wi-Fi, cellular, and competing drone signals. Physical terrain, buildings, and even the aircraft's own body can create shadowing that interrupts the link. Building lost link awareness into every pre-flight planning session — the same way a student pilot reviews emergency landing options before takeoff — is the mark of a prepared and legally compliant RPIC.

Key Numbers and Rules

14 CFR 107.19: RPIC is responsible for the safe outcome of the flight at all times, including during lost link events.
14 CFR 107.31: RPIC must maintain VLOS; a drone operating on failsafe does not relieve this requirement.
Failsafe link-loss timer: Typically 1–3 seconds on most platforms; configure per manufacturer guidance and local conditions.
RTH altitude: Must clear the tallest obstacle between the drone's last position and the home point — verify this before every flight at a new location.
Home point verification: Always confirm the home point is set at the actual takeoff location before committing to flight.

Common Test Traps

Assuming failsafe absolves the RPIC of responsibility. A lost link event does not transfer accountability away from the remote pilot. The FAA expects you to have planned for it.
Confusing lost link with loss of GPS. These are separate failures with different consequences. A drone can lose GPS and still be controllable; it can lose the datalink and still have full GPS function. Know which failure you are dealing with.
Relying on factory-default RTH altitude. Many platforms ship with an RTH altitude of 20–30 meters, which is adequate for open fields but will fly the drone directly into trees or structures at many real-world sites. Always adjust for local conditions.
Forgetting to re-verify the home point after repositioning. If you power on at your vehicle, walk 200 feet to the actual launch site, and take off, your home point may be at your car, not your feet. Test this on your specific platform before relying on RTH in an emergency.
Overlooking RF interference as a lost link cause. Test questions and real-world incidents frequently involve interference from Wi-Fi routers, power lines, and other drones. Knowing to identify and mitigate interference sources is part of the RPIC's pre-flight responsibility.