Grafair Hawker 800XP SE-RLX for the HTAI model.
These are textures only.
The HTAI BAe HS.125-800 model is required.
It can be found at http://htai-models.com/downloads.html
The converted P3Dv4 model can be found here:
https://www.alpha-india.net/forums/index.php?topic=26276
Flightplans available here: https://oneclickhangar.com/forum/index.php?topic=5570.msg7895#msg7895