Which type of airspace exists outside the boundaries of a nation and is not subject to state sovereignty?

The correct answer is international airspace, which refers to areas of airspace that extend beyond the territorial limits of any nation and are not subject to the sovereignty of any state. This airspace is governed by international agreements, primarily established by the Convention on International Civil Aviation, which aims to promote safe and orderly development of international civil aviation.

In international airspace, generally, nations have the right to overfly these areas without restrictions imposed by any specific country. This characteristic allows for freedom of navigation and flight, contributing to global connectivity and transport.

Other types of airspace, such as national airspace, are under the jurisdiction of specific countries, meaning that they impose regulations and controls over the operations within their borders. Zonal airspace is not a widely recognized term in aviation; therefore, it is not relevant in this context. Contested airspace refers to regions where nations may have conflicting claims of sovereignty, resulting in military presence or regulations, which is contrary to the notion of international airspace.