Which organization establishes technical specifications for radio aids to navigation in civil aviation?

The International Civil Aviation Organization (ICAO) is the body responsible for establishing and maintaining global standards and regulations related to civil aviation. This includes the formulation of technical specifications for radio aids to navigation, which are critical for ensuring safe and efficient air navigation.

ICAO's role in setting these specifications is crucial because it coordinates the efforts of member states and promotes compliance with international aviation standards. By crafting these specifications, ICAO enhances interoperability between different countries' navigation systems, which is essential for international flight safety and efficiency.

In contrast, while the Federal Aviation Administration (FAA) is responsible for regulating civil aviation in the United States specifically, its standards may not apply globally in the same way that ICAO's do. NASA primarily focuses on aerospace and space exploration rather than civil aviation navigation aids. The National Transportation Safety Board (NTSB) concentrates on investigating aviation accidents and making safety recommendations, rather than establishing technical specifications for navigation.

Thus, the answer correctly identifies ICAO as the organization tasked with these essential responsibilities in the realm of civil aviation navigation.