What type of permit is required for an aircraft not approved for return to service?

The correct choice is the Special Flight Permit, which is required for an aircraft that is not approved for return to service. This type of permit allows an aircraft to operate under specific conditions that do not meet the standard airworthiness requirements typically necessary for regular flight operations.

A Special Flight Permit is often issued for various purposes, such as allowing an aircraft to be flown for maintenance, to reposition it, or to deliver it to a location where repairs can be performed. It ensures that proper safety checks and protocols are followed, even when the aircraft isn't fully compliant with airworthiness standards.

Other options, such as Flight Plan Authorization, Temporary Flight Permit, and Maintenance Flight Permit, do not serve the same purpose. For instance, a Flight Plan Authorization is typically related to filing a flight plan with air traffic control, while a Temporary Flight Permit generally applies to aircraft that are in the process of obtaining airworthiness certification. A Maintenance Flight Permit can refer to specific regulatory stipulations for maintenance activities but does not encompass the broader needs addressed by a Special Flight Permit when dealing with aircraft not approved for standard operations.