Normally I like these, but I've seen this exact same concept before. (Google "Inside a Dead Skyscraper game" to find it). Once that novelty was over, the game wasn't that interesting aside from finding all the pieces. I wish you had more locations with meaning to visit, because that was the coolest and most touching part of the whole game to me. I feel like the previous game I mentioned had more impact on me, however, but it was shorter. (The feeling of WEE flight! was more well done in it as well.)
I also felt the ending was too long-winded. It was nice poetry, but I wish I could just use spacebar to read through it. I can read faster than that, and I know that at some parts you had to time it with the video, but other times it would've worked fine. I actually found myself browsing through other tabs waiting for a line to fade away.
Overall if you'd have fleshed this out more and made it more gratifying to fly/more things to discover (exploration was not rewarded, in fact the slow flight time made it a pain) I'd have not cared that this concept was done before. However, it wasn't really improved enough for me to think this above average. I'm sorry. =(
Although, I encourage you to do more stuff, because this was still a good distraction, it just needed more to it. =)