just a small translation " Erdogan arrives in Morrocco"

Erdoğan Fas´a geliyor.

Q: could you use inmek here?

If his plane is landing, maybe yes.

So there has to be the meaning of ´going down, landing´, tamam. TDK says one meaning of inmek is 

4. -e Bir yerden başka bir yere gitmek, varmak
"Bünyamin, gücünün yettiği kadar hızlı yürüyüp Haliç´e indi." - İ. O. Anar

and I thought it might be more general.

Hmm, yeah if you put it this way. Then you´re right. It´s not just landing. 

I think it is only for "going from high level into low level". As the example indicates, Bunyamin goes to Halic, most probably the seaside (low level). So it is "inmek"

In Arabic when you visit someone you can "descend to him". That is why I have paid attention to some uses of inmek and wondered if it is copying the same use. Quite interesting, thanks Faruk and caliptrix.

Erdoğan Fas´a varıyor.

Çarşıya inmek ve çarşıya çıkmak  both may mean "going to town center".

Generally speaking, the former one, if your starting point is at a higher elevation than the town center: the latter, if vica versa.

In Arabıc use, what the beduin who says "I descended to him" means is not "I descended on him" but "I descended from my camel at his place".