The standards and recommended practices (SARPs) of ICAO Annex 6, Part II are based on the State of Registry (SoR) principle.
The European rules for NCC operations are based on the State of the Operator (SoO) principle.
This does not constitute a contradiction to the Chicago Convention but rather establishes a complementary safety instrument, particularly when a European operator uses third-country registered aircraft.
The SoR is responsible for the oversight of the aircraft in its registry. The EU SoO is responsible for the oversight of operators having their principal place of business in an EU Member State. Although the EU SoO is the competent authority for the operators having their principal place of business in an EU Member State, the EU SoO and the foreign SoR should cooperate in order to ensure proper oversight of these operators, in compliance with the ICAO requirements.
When the SoR and the SoO are both EU Member States, they oversee the aircraft, as well as the organisations and personnel involved in their operation in a complementary manner and according to the same rules. The European regulatory framework permits both the SoR and the SoO to duly exercise their respective oversight responsibilities and to take the appropriate enforcement actions. Oversight and enforcement are therefore ensured at all times, irrespective of the EU Member State in which the aircraft is registered or where the operations take place. It is at all times legally clear which EU Member State is responsible for each aspect of the safety oversight of any aircraft registered in an EU Member State and operated by an operator having its principal place of business in an EU Member State acting as SoO.