In an in-flight emergency requiring immediate action, the remote pilot in command may deviate from any rule of Part 107 to the extent necessary to meet that emergency. That authority is §107.21(a). It is limited to what the emergency requires. It is not prior permission, and it is not a license to hand the controls to a bystander. If the pilot deviates, §107.21(b) requires a written report of that deviation to the Administrator, upon the Administrator's request.
What the deviation covers
The trigger is an in-flight emergency that requires immediate action. The scope is any rule in Part 107, and only to the extent necessary. A pilot who needs to leave a planned corridor to keep the aircraft away from people may do that without waiting for a written approval. A pilot who wants a standing permission to fly the same profile next week is describing a waiver, not an emergency.
The wrong readings are easy to spot. The remote pilot does not satisfy §107.21 by handing the transmitter to any bystander. The remote pilot does not need a letter in hand before the deviation. The person who holds this authority is the remote pilot in command, whose ordinary duties are described on the remote pilot in command page. Those duties include planning so a loss of control would not create an undue hazard. Section 107.21 is what remains when the emergency is already happening.
People and property come first
During a genuine in-flight emergency near people, the first priority is the safest action that protects people and property, including a deviation from the plan. Completing the scheduled shots is not the priority. Continuing to film until the battery dies is not the priority. Section 107.21 exists so the safe action is available even when it crosses a rule the plan was built to follow.
Walk through a motor failure over a park path. The briefed route stayed over an empty field. The aircraft is now descending toward the path. The pilot turns it toward the empty grass, even though that turn leaves the corridor drawn on the shot list, because that is the move that keeps the aircraft off the people. The deviation matches the emergency. It does not authorize a scenic detour once the aircraft is stable and the people are no longer at risk.
Lost-link behavior should already have been set so the automatic path itself is the safe action. How to think about that failsafe before the emergency is on the lost link page. Section 107.21 does not replace that planning. It covers the moment planning was not enough.
The report, and the separate accident clock
Paragraph (b) is a request-driven report. Each remote pilot who deviates under paragraph (a) must, upon request of the Administrator, send a written report of that deviation. Silence from the FAA is not a hidden duty to mail a narrative on a timer the section does not contain. If the Administrator asks, the pilot writes it.
A different section starts when someone is hurt or property is damaged. Section 107.9 requires a report no later than 10 calendar days after an operation involving serious injury or any loss of consciousness, or damage to property other than the small unmanned aircraft above the $500 thresholds in that section. An emergency deviation that also injures a person can trigger both: the §107.21 report if the Administrator requests it, and the §107.9 report on its own calendar. The injury report is explained on the accident reporting page. Do not collapse the two into one form or one deadline.
A laser on a manned approach
One assigned item is a hazard report, not a §107.21 deviation, and it should be answered on its own facts. A tower controller reports that a manned aircraft was illuminated by a laser during an approach. If the drone crew has relevant information, report the illumination promptly to air traffic control or law enforcement and avoid the area. Laser illumination is a serious aviation hazard. Continuing because a drone is not piloted from onboard misses the point. Posting the aircraft's position online is not the report. Do not confront a suspected source.
The pattern across these items is the same priority. Meet the emergency to the extent necessary, protect people and property, tell the authority who needs the fact, and do not invent a permission slip the rule does not require before you act.
Use the free practice test for the emergency items. The course at pricing covers the decision in the operations lessons.