We do not have enough data on this route to provide a reliable graph showing how many days before departure it is the best to book.
However, usually the closer it is to the departure, the more expensive the tickets are.
The cheapest flights are on the route Costa del Sol (AGP) - Dortmund Airport (DTM).
Direct flights last about 3h 5min.
Direct flights available 2 days a week - Tuesday, Saturday.
Direct flights: Ryanair (FR).