Lost Link Procedures
A "lost link" is one of the most common non-normal events a remote pilot will encounter, and unlike a true fly-away (covered in the next lesson), it is usually the most survivable one — if the remote pilot has actually taken the time to understand and prepare for it beforehand. This lesson has no dedicated Part 107 regulation number of its own; instead it is grounded in 14 CFR 107.21's deviation authority and 14 CFR 107.19's ongoing responsibility for the remote pilot in command to prevent undue hazard if control is lost.
Defining "lost link" precisely
A lost link occurs when the command-and-control (C2) radio link between the ground control station (the controller) and the small unmanned aircraft is interrupted — the aircraft can no longer receive commands from the remote pilot, even though the aircraft itself may still be flying normally in every other respect. This is distinct from a true fly-away, covered in the next lesson, where the aircraft is not simply out of communication but is actually behaving erratically or uncommanded in a way that a restored link would not necessarily fix.
14 CFR 107.19: the ongoing responsibility that makes lost-link preparation mandatory
14 CFR 107.19 establishes that a remote pilot in command must be designated for every flight, is directly responsible for and the final authority over the operation, and — critically for this lesson — must ensure that the small unmanned aircraft will pose no undue hazard to other people, other aircraft, or other property in the event of a loss of control of the aircraft for any reason. That last clause is exactly what a lost link is: a loss of control. 107.19 does not merely permit thinking about what happens if the link is lost — it requires the remote pilot to have already ensured, before the fact, that a loss of control will not create an undue hazard.
Failsafe behavior: what the aircraft does when it can't hear you
Virtually every consumer and commercial small UAS has a configurable failsafe behavior that activates automatically when the control link is lost, since the aircraft cannot simply wait indefinitely for a lost signal to return. The three most common failsafe behaviors are return-to-home (the aircraft climbs to a set altitude, if needed, and autonomously flies back to its recorded launch or home point and lands), hover-and-land (the aircraft holds its current position for a set time, hoping the link returns, then lands in place if it does not), and continue-mission (rare, and mostly limited to specific autonomous survey or mapping profiles, where the aircraft keeps executing a pre-programmed flight plan). Meeting the 107.19 undue-hazard duty means the remote pilot must know, before flight, exactly which of these behaviors is configured, and must confirm that behavior would not create a hazard given the specific flight's location and surroundings.
- Return-to-home: requires an accurate recorded home point and enough battery reserve to complete the return; a poorly set home point can cause the aircraft to attempt to fly back through, rather than around, an obstacle.
- Hover-and-land: can be safer over an area with obstacles below, but risks the aircraft simply landing wherever it happens to be, which may not be a safe surface.
- Continue-mission: demands the highest confidence in the pre-programmed flight path, since no pilot correction is possible until the link is restored.
Worked scenario: choosing a failsafe setting for a specific site
You are preparing to fly a mapping mission over a large, open agricultural field with no significant obstacles between the flight area and the launch point. A return-to-home failsafe is a strong choice here: the flight path back to the recorded home point is unobstructed, and the aircraft has ample open space to descend safely if it needs to. Contrast this with a tightly bounded urban rooftop inspection surrounded by taller buildings, where a return-to-home climb-and-fly-back could carry the aircraft directly toward a structure it cannot see and avoid on its own — there, a hover-and-land failsafe, paired with a carefully chosen flight altitude that keeps the aircraft below surrounding rooflines, may better satisfy the 107.19 undue-hazard duty for that specific site.
The three common lost-link failsafe behaviors a remote pilot must understand and configure appropriately before flight.
View LargerMost lost-link events never require invoking 107.21
If the aircraft's failsafe behavior activates and successfully resolves the situation — returning home and landing without incident, or landing safely in place — no Part 107 rule has actually been violated, and 14 CFR 107.21's deviation authority was never needed. This is the outcome a well-configured failsafe and a carefully chosen flight location are designed to produce.
When it might be needed
107.21 becomes relevant if regaining control, or safely resolving the loss of control, genuinely requires deviating from a Part 107 rule — for example, if reestablishing the link requires briefly repositioning in a way that would otherwise conflict with a specific rule, or if an unanticipated obstacle in the failsafe's path forces the remote pilot to take manual action outside the original flight plan the moment the link happens to reconnect. In those genuine emergency situations, 107.21 authorizes the deviation necessary to meet the emergency, and 107.21(b)'s written-report duty would apply if the FAA later requests one.
| Failsafe behavior | Best suited for | Key risk if misconfigured |
|---|---|---|
| Return-to-home | Open areas with a clear path back to the launch point | Flying into an obstacle along the return path or an inaccurate home point |
| Hover-and-land | Tightly bounded or obstacle-dense sites where a long autonomous flyback is risky | Landing on an unsafe surface directly below the current position |
| Continue-mission | Pre-validated, fully autonomous survey or mapping flight plans | No pilot correction available if the pre-programmed path encounters an unexpected hazard |
Preparing for and Responding to a Lost Link
A practical sequence covering both preflight preparation and in-the-moment response.
Know your aircraft's current failsafe configuration before every flight
Confirm which behavior is set — return-to-home, hover-and-land, or continue-mission — rather than assuming a factory default that may have been changed.
Evaluate whether that behavior fits the specific site
Consider obstacles, terrain, and surrounding hazards along the failsafe's likely path or landing footprint, and reconfigure it if the default doesn't fit this particular flight.
Confirm the recorded home point is accurate immediately before launch
A home point recorded at the wrong location can send a return-to-home failsafe toward an unintended, potentially unsafe, destination.
If the link is lost in flight, resist the urge to immediately fight the controller
Give the configured failsafe a moment to activate as designed rather than assuming it has failed within the first second or two.
Maintain visual contact and monitor the aircraft's behavior
Keep watching the aircraft to confirm the failsafe is actually executing as expected, ready to take manual control the instant the link reconnects.
Document what happened once the aircraft is safely on the ground
Note the cause if known, the failsafe behavior that activated, and the outcome — useful both for future prevention and in case an 107.21(b) report is later requested.
| Mistake | Why it happens | Correct understanding | Regulation / source |
|---|---|---|---|
| Assuming the factory-default failsafe setting is automatically appropriate for every site | The default works most of the time, so it feels safe to leave alone | 14 CFR 107.19 requires the remote pilot to ensure no undue hazard results from a loss of control at this specific site, which may require changing the default. | 14 CFR 107.19 |
| Immediately assuming a fly-away the instant the link drops | The sudden loss of control feels alarming | A lost link with a properly configured failsafe usually resolves itself; a true fly-away (Lesson C) is a distinct, less common situation. | 14 CFR 107.19 |
| Believing every lost-link event automatically invokes 14 CFR 107.21 | Any control-related problem feels like it should count as an "emergency" | 107.21 only applies if a deviation from a rule becomes necessary; a failsafe that resolves the event without a rule violation does not invoke it. | 14 CFR 107.21 |
| Not verifying the home point immediately before launch | Treating home-point recording as a one-time setup step | An inaccurate home point can send a return-to-home failsafe toward an unsafe or unintended location. | 14 CFR 107.19 |
Does Part 107 specify exactly what a lost-link failsafe must do?
No. Part 107 has no dedicated regulation prescribing failsafe behavior. The requirement flows from 14 CFR 107.19's duty to ensure no undue hazard results from a loss of control, which the remote pilot satisfies by configuring and verifying an appropriate failsafe for each specific flight.
Is a lost link the same thing as a fly-away?
No. A lost link means the control link is interrupted but the aircraft is executing a known, predictable failsafe behavior. A fly-away, covered in the next lesson, means the aircraft is behaving unpredictably or uncommanded in a way a restored link would not necessarily resolve.
Should I always choose return-to-home as my failsafe setting?
Not necessarily. Return-to-home works well in open areas with a clear path back to the launch point, but it can be less appropriate in obstacle-dense or tightly bounded sites, where hover-and-land may better satisfy the 107.19 undue-hazard duty.
Test Your Knowledge
Answer the questions below to check your understanding. Every answer can be found in the lesson above.