Ownership Type = 'Not Operator' is used when aircraft have been added into an Airline Profile from the Subsidiary Airlines filter. These are airlines that are part of the same operator group as the selected airline, e.g. Iberia Express is a subsidiary of Iberia. The additional aircraft displayed all have a role association with the selected airline (Owner, Manager, Sub-Lessor, etc), so can be considered to be part of its fleet. To analyse aircraft Ownership Types for a subsidiary airline, run a separate Airline Profile for the required airline.
Airline Profile Ownership Type definitions can be found at https://profiles.cirium.com/assets/airline-fleet-glossary.pdf
Lessor Profile Ownership Type definitions can be found at https://profiles.cirium.com/assets/lessor-fleet-glossary.pdf