Thanks for the reply, FearlessFrog. I have updated everything and WT3 works perfectly fine on its own. I am trying to do what you suggested at the top of this forum i.e. get WT3 aircraft into X-plane 11 AI. I have no problem finding the World Traffic (Other) folder to select for AI. The problem is that the planes do not appear in the sim. Their cross shape appears in the map in X-Plane, but there are no lanes in the sim.
I think quite a lot changed since I wrote that, so not sure you even need to add AI flights anymore, as X-Plane introduced a TCAS API for plug-in authors to use. There is this section here (but I haven’t tried it, as not done this is a while):
If you’re not using P2ATC, delete this file: X-Plane 11\Aircraft\Classic Jet Simulations\WorldTraffic\AIplane.acf It’s not needed anymore with the new TCAS system. If you have been using WT 3.2.0b13 or WT 3.2.0RC1/RC2, skip to step 5. If you are using P2ATC then keep the file as P2ATC still requires that 19 X-Plane AI planes should be defined so set them to the WT AI plane.
If you delete that file, Alplane.acf, the World Traffic (Other) option no longer appears in the AI menu. Perhaps it is no longer possible to use WT3 planes in this way. There is an airplane AI on the X-Plane forum that works pretty well and is not too much of a drain on resources. I wanted to test the WT3 planes to see if they are even less of a drain on resources. Oh well. Thank you for all of your help.