IR missiles of some vehicles do not react to countermeasures at all

Well, the topic says it all…

I can name the PGZ04A, or the Ozelot… I can empty all my countermeasures in one go, the missile tracks me and never misses.

You’re not defending against them properly. Both use FOV tightening and tracking suspension.

The way this works is post launch the FOV of the seeker on the missile is much smaller than prelaunch. The reduced FOV means the flares are less likely to be seen in the FOV of the seeker and decoy the missile.

The second technique is tracking suspension. When a flare enters the FOV of the seeker it stops tracking briefly and uses the targets last known inertia to maintain lock, after a second or two tracking will start again if the target is still within the FOV.

To defeat such ECCM features you first should avoid being in range. Second if you need to be in range pre-flaring using continuous release is the best defence as it will prevent the missile from locking you effectively to begin with.

If you’ve been fired on, flare but don’t change course at the same time. You need to flare then maneuver. If you flare and maneuver at the same time the inertia from your maneuver will keep the seeker on you. Depending on your range to the target and your ability to complete the require defensive maneuver in time before impact will determine if you die or not.

Thanks for the elaborate manual:]
I will try your recommendations…
But factually, when I release all of my countermeasures in one second (just spam the button) in such a way, that I can’t see my own plane through them, I would assume that there would be a certain probability that the missile would follow a fake target and explode somewhere next to me.
In case of the PGZ04A, my experience is that no matter what I do, the missile hits the geometrical center of my plane…
While other AA systems do react to this method and the missiles, while already in the air, do sometimes target the countermeasure and explode not necesarilly pixel perfect in the center of my plane :]
I can accept that some IR systems are better, some worse. But the PGZ04A and the Ozelot seem to have an unrealistic edge.

With seeker suspension the idea is that they never follow a flare. Presence of a flare suspends tracking. So it doesn’t “go” for flares the same way a AIM-9L would for example.