"We fly our rockets from the military firing practice area ES D 139 in the Baltic Sea, 20 km east of of the Danish island of Bornholm. It spans 70×35 km, and are opened to us by the Royal Danish Navy for the launch time window. The Danish and Swedish authorities are very helpful, and close the airspace above for airtraffic in the hours of the actual launch."
https://copenhagensuborbitals.com/about-us/