The owner of the aircraft. The operator of the aircraft. The manufacturer of the aircraft.

Only when the operator will be paid for commercial services. All civilian small UAs weighing greater than .55 pounds must be registered regardless of its intended use.  When the small UA ...

0.55 pounds or less.  0.75 pounds or less. 0.65 pounds or less.

Operating your sUAS for an imagery company.   Flying for enjoyment with family and friends. Conducting public operations during a search mission.