• 航空こうくう — aviation
• 航海こうかい — voyage, sailing
• 航行こうこう — navigation, sailing
• 回航かいこう — ferrying a vessel
• 航路こうろ — route (for ships or planes)

航 is a 形声文字 (semantic-phonetic compound). The left side 舟 means "boat," and the right side 𠦝 (phonetic component カウ／コウ) hints at the pronunciation. Together, they describe movement via boat — thus implying navigation across water or air.

航空機こうくうきは 時間じかんどおりに 到着とうちゃくしました。
The aircraft arrived on time.

彼かれは 航海士こうかいしとして 働はたらいています。
He works as a navigator (sailor).

The on-yomi コウ is used in all vocabulary words. There is no common kun-yomi for standalone use. 航 usually appears in compound terms related to water or air navigation.