Airspace can be temporarily closed or restricted due to, for example, military exercises.
Per NOTAM, GND/2000FT AMSL
Click on the map for high resolution.
For a full and up-to-date overview of temporary airspace restrictions, contact your own Flight Information Office. Also see NOTAM's en AIC's.
For Dutch airspace alerts you can download the NL Airspace AVOID app. Go to www.airspaceavoid.com