is the infinitive ''kontrol etmek'', if so what does it mean
I means "to check", "to control", etc.. Take a look here: http://tureng.com/en/turkish-english/kontrol%20etmek
If it's like the French "controler", then English "control" might be a false friend and "check, inspect" are better - "control" means more like "steer, rule, direct".
This is something almost universally difficult for anyone learning a language influenced by French. :D
It means both!
Uçağı kontrol ediyorum. - I am controlling/checking the airplane.
We understand what it means by the context.
Why is "I am taking control" wrong? How would you say it?
That means something totally different in English. (Estoy tomando contol). In Turkish, it would be something like "başa geçiyorum"
"kontrol etmek" is like "inspeccionar" and less like "to control" in English (unless you are going through passport control)
Ok. Is "I am monitoring" accepted?
I would translate "to monitor" more as "izlemek," as that has more to do with watching. "kontrol etmek" is like going through something to find mistakes.