14 CFR §135.105

1. (a)Except as provided in §§ 135.99 and 135.111, unless two pilots are required by this chapter for operations under VFR, a person may operate an aircraft without a second in command, if it is equipped with an operative approved autopilot system and the use of that system is authorized by appropriate operations specifications. No certificate holder may use any person, nor may any person serve, as a pilot in command under this section of an aircraft operated in a commuter operation, as defined in part 119 of this chapter unless that person has at least 100 hours pilot in command flight time in the make and model of aircraft to be flown and has met all other applicable requirements of this part.
2. (b)The certificate holder may apply for an amendment of its operations specifications to authorize the use of an autopilot system in place of a second in command.
3. (c)The Administrator issues an amendment to the operations specifications authorizing the use of an autopilot system, in place of a second in command, if—
   1. (1)The autopilot is capable of operating the aircraft controls to maintain flight and maneuver it about the three axes; and
   2. (2)The certificate holder shows, to the satisfaction of the Administrator, that operations using the autopilot system can be conducted safely and in compliance with this part.