Upvote:0
You will not need an airport transit visa because you will have a short-stay type C visa. You will enter the Schengen area in Munich and leave it in Frankfurt. There will be no "systematic" passport control in Spain, though there is a chance that you'll encounter a less formal check.
Upvote:5
Both Spain and Germany are in the Schengen travel area. You will enter the Schengen area in Munich and go through immigration controls there, and leave again from Frankfurt. The flights from Germany to Spain are effectively domestic flights.