This would be the captain in a typical two- or three-pilot aircrew, or "pilot" if there is only one certificated and qualified pilot at the controls of an aircraft. The PIC must be legally certificated (or otherwise authorized) to operate the aircraft for the specific flight and flight conditions, but need not be actually manipulating the controls at any given moment. The PIC is the person legally in charge of the aircraft and its flight safety and operation, and would normally be the primary person liable for an infraction of any flight rule.