What I now do exploring the Flying Fortresses is this:
I first turn into a dragon and fly around to explore the area and look where I wish to begin in humanform. Then I destroy all dragon defences (balista's, nests, etc) of the flying platform EXCEPT 1 Balista !
Then I turn back in human and explore that platform ...

If I go back to the Orobas Fjords and , let's say a few days/weeks or more, back to that FF I can see immediately which flying platform I did the last time I was there.
wink

On 7th of february 2015 : I start a new adventure in the Divinity world of Original Sin,
it's a Fantastic Freaking Fabulous Funny ... it's my All Time Favorite One !