Section 107.23(a) prohibits operating a small unmanned aircraft system in a careless or reckless manner so as to endanger the life or property of another. The remote pilot in command remains directly responsible for that flight under §107.19, including when a visual observer is supposed to be scanning and when a company owns the aircraft. A legal hover becomes a hazardous operation the moment the pilot holds position in front of arriving traffic or launches with a lost-link path aimed at people.
What the hazardous-operation rule covers
The prohibition is aimed at the manner of the operation and at the danger it creates for someone else's life or property. It sits next to a separate sentence, §107.23(b), about dropping objects. Dropping is its own rule on the dropping objects page. Careless or reckless flight is this one.
Section 107.19 is how the FAA names the person who has to prevent that flight. A remote pilot in command must be designated before or during the flight. That pilot is directly responsible for, and is the final authority as to, the operation. The pilot must ensure the small unmanned aircraft will pose no undue hazard to other people, other aircraft, or other property if control is lost for any reason. The pilot must ensure the operation complies with the applicable regulations, and must be able to direct the aircraft so that compliance actually happens.
The visual observer does not take the responsibility
During a bridge inspection the visual observer fails to notice a helicopter, and the remote pilot has to maneuver hard to avoid it. The person responsible for the safe operation was the remote pilot in command. Section 107.19(b) does not move that duty onto the observer because scanning was the observer's assigned task, and it does not split the duty into equal shares. The company that hired the crew does not become the remote pilot either. Crew resource management still matters. The observer should have called the traffic. The regulation's answer to "who was responsible" stays with the pilot in command. The duties of that role are laid out on the remote pilot in command page.
Plan the failure before you launch
Before a roof inspection, the remote pilot notices that a lost control link would send the automatic return-to-home path directly over a crowded sidewalk. Section 107.19(c) requires the pilot to ensure that a loss of control, for any reason, would not pose an undue hazard to people, other aircraft, or property. The practical step is to change the plan before launch: move the launch point, or change the failsafe routing, so the aircraft's uncommanded path stays clear.
A return-to-home function does not count as maintaining control. The duty applies before the motors start, not only after a link has already failed. The rule does not tell the pilot to file a hazard notice with air traffic control as the substitute for a safe route. Automation that flies a grid does not retire the duty either. The pilot still has to be able to direct the aircraft.
Yielding is part of staying clear of the rule
A survey drone has been hovering legally near a small heliport for ten minutes when a medical helicopter approaches to land. Section 107.37 requires the small unmanned aircraft to yield the right of way to all aircraft. Yielding means giving way, and not passing over, under, or ahead of the other aircraft unless well clear. Section 107.43 separately prohibits operating in a manner that interferes with operations at any airport, heliport, or seaplane base.
The helicopter does not have to give way because the drone was established in the area first. Remaining below 400 feet, or remaining outside controlled airspace, does not create a right of way either. The pilot who keeps the hover because "we were here first" is describing the conflict §107.23 is written to stop. Give way, and stay well clear of the approach. How that yield works in more detail is on the right-of-way page.
Picture the same site with the helicopter still two miles out and higher than the drone. Holding altitude because the traffic is not at your height yet leaves you in the descent path. The move that matches both sections is to reposition early, well clear of the pattern and the final approach, and to keep the ability to see the helicopter while you do it.
These three ideas travel together on the knowledge test. The remote pilot owns the flight. The lost-link path is planned so it does not endanger anyone. Other aircraft get the right of way. Use the free practice test on this set, and follow the operating-rules lessons in the course at pricing.