While adding several military fighters to an airbase -mostly Mike Pearson AI - I noticed that the Mirage III (French Air Force) were NOT holding short of the line before take-off. They keep going right into one another....merging together!!
I even tested the Royal Australian Airforce Mirage III models....SAME thing.

Yes, I have double-checked that the RED hold-short node is correctly linked to the runway.
But I have no clue what might be causing this anomalous behaviour in MPAI Mirage III aircraft.

Further testing with other AI produced correct behaviour: the AI do hold-short of the line and do NOT cross over until cleared for take-off.
Both the MPAI F-104 Starfighters and the FMAI Mirage 2000 hold short properly, behind the lines. Perfect performance by both models!!
The screenshots below confirm this...so it does not seem as if the afcad itself is causing this irregularity, or other AI would imitate the Mirage III anomalous behaviour.
After changing the Mirage III "airfile" with that of another AI model plane, the problem persisted.

However, one never knows enough when it comes to FS9, so there might be something I've missed or do not know behind this...

After some more investigating....the problem is SOLVED.

In the aircraft config file there is ONE parameter that I tweaked:

[brakes]
toe_brakes_scale = 0.01 (ORIGINAL value)

This is the NEW value (which I copied from the MPAI Mirage IV model which DID hold-short correctly);

[brakes]
toe_brakes_scale = 0.75 (NEW value)

When I tested Mike Pearson's "Mirage IV" model, there was no problem.
Comparing the aircraft config files of BOTH aircraft - the MPAI Mirage III and the MPAI Mirage IV - models,
I noticed the big difference in the value set for the "toe_brakes_scale".
So I decided to tweak just this one parameter, then see what happens....

Apparently, this was the cause of the problem.

That 0.01 toe brakes scalar setting could certainly cause that problem and was probably intended to be 0.1 by the AI FDE creator. Often times the toe brakes scalar is reduced in AI FDE's to prevent too much of a nose dip when the AI slows or stops on the ground, but obviously 0.01 is going a bit too low. I usually set the toe brakes scalar for my AI FDE's at between 0.25 and 0.50 with no problems.