Starflight does not use separate save files, but rather modifies its files to store a universal "gamestate". The original intention was to make the game's world "evolve" during play, and be consistent.
To access the directory the save states and settings are stored open the terminal and type:
open ~/"Library/Application Support/Boxer/Gamebox States/com.gog.starflight-1"
Make a backup of this folder after saving a game so you can restore it in case of death.