Tittle. Are the missions always the same, or they have some random elements? I'm worried about replay value of this game before purchase

The missions are all pre-scripted. I did not notice any variation, but perhaps is me.
Truth is, that there are 16 training missions, 14 missions from Iraq and a undisclosed number of Flight of the Old Dog campaign missons.

In addition, there are two addons, with a number of additional missions.

All in all, you will have 50 missions, give or take, with increasing difficulty and some story to be told.
Quite a long time to play all of them.

And for the price, can't see how it can go wrong.