Yes, it is different situations really. The movement around the map is done by scripts and routines to give the semblence of "life" on the map. To compare it with CloD you would have to only look at the part where they interact with the player (as the movement around the map without player input in CloD is one by waypoints and scripts/triggers and is manually done).

Therefore what does the AI of STALKER or Skyrim have to take into account? Position of the player and their position, perhaps in Stalker there is the use of cover and ammunition- I dont recall if they can run out of weapon ammo etc.

In CloD there are far more variables- multiple enemies, engine situation etc once the enemy has "seen" the player and decided to enter or flee combat. Therefore a simplified routine is used. It needs developing but it is not a system that is less complex than the AI of FPS shooters, especially when you consider the other systems being modelled concurrently- engine states, flight models, damage models etc which aren't present in games like Skyrim.

Guys, you are NOT programmers, and you DO NOT have any idea how or even what AI programming really is.

You are keep talking about internal systems, but that has NOTHING to do with the AI system. they are two different things. AI system can use input from the internal systems of a plane, but that's it.

Do you have any idea how many states, or parameters has a human NPC agent from Skyrim?!! Obviously you don't!

STOP embarrassing yourselves, and listen to what someone who knows this stuff is saying about.

IL2CLOD's AI IT IS NOT MORE COMPLICATED THAN MOST OF THE AI's OF OTHER GAMES! PERIOD!

PS: ANY decent game has AI agents having multiple states, tens of parameters, account multiple enemies, know and use the terrain (Il2CoD doesn't), know and use dynamic collision objects (a thing which actually IL2COD is not doing, as they don't care about the clouds), has to decide when to switch from a finite machine state to another, has to account ammunition, work in team, know the state of a mount/pet/companion (IL2CoD's pilot/plane relation), etc, etc.

First STALKER Shadow of Chernobyl was a lot like CloD when it was released back in 2007. Developed by Ukrainian studio it was delayed several times. It was an incredibly ambitious project and management had to force developer to cut plenty of content only to get the game into releaseable state. On release Stalker was plagued by bugs and poor framerates but after several patches and with community made mods it is easily one of the best games i have ever played. I do not know how things will turn up with CloD but i hope it will become the best flight sim ever.
On topic now from wikipedia
So no scripts my friend STALKER AI is an achievement and also probably one of the things that delayed development.
I believe that Maddox Games had the same problem as STALKER devs. They set way to ambitious goals and they could not do it everything. Resulting in publisher pressuring them to release unfinished game in hope to get back their investment.