SPATO (Single Pilot Air Taxi Operator)

A SPATO (Single Pilot Air Taxi Operator), according to the FAA is a certificate holder who uses just one pilot for Part 135 operations. In other words, the only pilot who can fly a Part 135 trip is named in the authorization's Operations Specifications; no other pilot, freelance or temporary employee, can fly on that authorization.

ource

Wayne Phillips "AOPA Flight Training" June 1995