Here's some related information from the TTools ReadMe file:

23. Guidelines for adding aircraft
A large number of add-on aircraft have problems when used as AI aircraft. The main problems are: missing landing gear, crash landings, and bad frame rates. All of these problems can be avoided by using add-on aircraft that are specifically designed for AI use. The Project AI group (PAI) have a very large array of aircraft, all designed to be used as AI problem-free. I highly recommend that you use this source of freeware add-ons whenever possible.

If you decide to use add-on aircraft that were not designed specifically for AI use, then you better read the remainder of this section, and be prepared for some trail-and-error

21. FlightPlans...txt File
Aircraft tag:
This is used strictly by the compiler. It specifies which aircraft in the Aircraft...txt source file to use with this flight plan. You can use any aircraft from the associated Aircraft...txt file, but the flight plan parameters, especially the altitude, trip distance, and flying time should be realistic for the type of aircraft used.

. . . additional info is available in the TTools' manual

bill