This is a frustrating series because it had so much promise. The artwork and animation are superbly detailed. I couldn't believe I was watching an anime produced 8-9 years ago. The premise and story are pretty interesting as well, though somewhat disjointed. It felt like a love letter to the art and culture of air flight, but then that line clashes a bit with the whole sci-fi aspect of the series. The ending also feels abrupt and rushed. It felt like the story took an abrupt turn, the way that James Cameron's "The Abyss" did. But the ending wasn't built up the same way, leading to the rushed feeling at the end.
On the bright side, not only does the artwork shine, but there are a few bright dramatic moments where the director builds the scene to an impressive crescendo. And on the dark side, the dialogue also suffers from the same disjointedness that the plot does.