The FAA uses whose definition and severity categories for runway incursions?

The correct answer is based on the fact that the FAA aligns its definitions and severity categorization for runway incursions with the International Civil Aviation Organization (ICAO). ICAO provides a standardized framework that is accepted and utilized globally in the aviation industry. By adopting ICAO's definitions, the FAA ensures consistency in the classification of runway incursions, which is vital for international aviation safety and communication. This alignment facilitates a clearer understanding of the issues at hand among various aviation stakeholders, ultimately enhancing safety regulations and operational practices.

In contrast, the FAA and NTSB have their own roles and definitions, but for the specific context of runway incursions, the ICAO's definitions are recognized as the baseline. A Certified Flight Instructor (CFI) focuses more on teaching and training aspects rather than defining operational safety standards like runway incursions. Thus, adhering to ICAO's standards helps to maintain a unified approach to aviation safety worldwide.