To avoid a possible collision with a manned airplane, you estimate that your small UA climbed to an altitude greater than 600 feet AGL. To whom must you report the deviation?

Why →Under 14 CFR § 107.21, a remote pilot may deviate from Part 107 rules to the extent necessary to meet an emergency. After the emergency, the remote pilot must, upon request from the FAA, send a written report. The report is not automatic. It's only required if the FAA asks for it.

The trap →You do NOT automatically call ATC or the NTSB. The NTSB handles accident investigations for crashes with injury/damage. ATC is for manned aircraft communications. FAA deviation reports under § 107.21 are submitted only when the FAA requests them.

Field note →This question tests a nuance: deviation reporting is reactive (only if asked), not proactive. Compare this to accident reporting under § 107.9, which IS immediate and automatic when serious injury or $500+ property damage occurs.