1. Air traffic management network functions shall lead to the sustainable and efficient use of airspace and of scarce resources. They shall also ensure that airspace users can operate environmentally- and climate-optimised flight trajectories and profiles, while allowing fair and reasonable access to airspace and air navigation services and minimising congestion. The network functions set out in paragraph 2 of this Article shall support seamless access to air navigation services by airspace users as well as the achievement of the Union-wide performance targets, referred to in Article 21(3), point (b), and shall be based on operational requirements. The implementation of those network functions shall respect the provisions of Article 1, and shall be without prejudice to Member States’ sovereignty over their airspace and to their requirements relating to public order, public security and defence matters.