‘Sub-orbital activities’ – the application of ‘international law’ in the twilight between air and space law

‘Sub-orbital activities’ – also referred to as ‘high altitude activities’, ‘higher airspace operations’ or ‘non-orbital spaceflight activities’ – are difficult to grasp from a legal perspective. Are they ‘aviation activities’ – governed by national and international air law – or are they ‘space activities’ – governed by national and international space law? The Space Law Committee of the International Law Association (ILA) has worked on this topic for more than a decade and finally adopted ‘Rules on Non-Orbital Spaceflight Activities’ at its 2024 Biennial Conference in Athens. One of the issues discussed was whether and to what extent ‘international law’ should be applicable to such activities. The present paper re-capitulates arguments in favor and against this idea and sheds some light upon relevant legal issues, such as state responsibility and liability, as well as on the role of commercial actors, in the twilight between air law and space law. • Application of international or national law to commercial human spaceflight • Recent adoption of the ILA Resolution on non-orbital spaceflight • Analysis of terminology of suborbital/non-orbital/high altitude/higher airspace • Relevance of air law and space law for commercial human spaceflight • Comparative analysis of different regulatory frameworks