It's sequential through single race for each speed class.
To unlock the craft, complete single races with each craft on a single track. eg. race feisar, pirhana (sic), auricom, qirex on porto kora venom
you will then unlock the next ship in the list for all tracks.
To unlock the tracks play them in order with one craft - porto kora, mega mall, etc until you finally unlock terminal.
These are independent of speed class - you will need to unlock ag systems again for phantom, or terminal again for phantom
If I remember correctly, it's faster to play through the selection diagonally: win the first one with Feisar, then the next one with (was it Qirex?). Anyway, keep getting golds diagonally through the ships and tracks to unlock the next speed class. I think? Sorry I can't fire up the game to check what I'm talking about...hope you get what I mean.