IPA: /ˌɛrəˈnɔːtɪkəl/
KK: /ˌɛrənɔˈtɪkəl/
Relating to the science and technology of flying and aircraft.
She is pursuing a degree in aeronautical engineering.
Aeronautical is formed from "aero-" (from Greek "aēr", meaning air) and "nautical" (from Latin "nauticus", meaning relating to ships or navigation). The word refers to anything related to the science or practice of flight in the air.
Think of 'air' ('aero-') and 'navigation' ('nautical') together to remember that 'aeronautical' relates to flying and navigating in the air.