The development of civil aviation in the early 20th century presented a range of new legal and regulatory challenges concerning the rights of an aircraft from one state to enter the aerial territory of another. International flights threatened the territorial integrity of nation states and prompted politicians to draw up new aerial legislation and regulations to govern this new form of aerial movement. Whereas some states advocated free and open access to airspace and unrestricted aerial movement, other nations pursued a more protectionist stance based on regulation and reciprocal access arrangements. Technological developments in aircraft design and performance, combined with changing global political relations and the introduction of new forms of economic regulation have all fundamentally affected the development of air transport.