溯る[sakanoboru] to go back
溯及[sokyuu] tracing back
溯源[sogen] returning to the origin

溯航[sokou] going upstream
溯河魚[sakkagyo] anadromous fish (fish that migrates upstream, e.g. salmon)

運航[unkou] operating (e.g. ships, aircraft)
えい航[eikou] towing (a ship)
英国航空[eikokukoukuu] British Airways
往航[oukou] outward voyage
廻航[kaikou] navigation

寄航[kikou] stopping at a port
休航[kyuukou] suspension of sailings
近接航空支援[kinsetsukoukuushien] close air support
欠航[kekkou] flight cancellation
航宇[kouu] aerospace