UFO?!

No photos this time... :)
February, 2005 - I made this video (a very long time ago, I know!) from my window. This is a shortened version (featured here) of the original, which you can watch here.
I submitted it to several people who supposedly know quite a bit about possible UFOs... No one could ever tell me what this is... There was no sound from above, only from traffic passing by on the street below...
What do you think it is?

Tags: ufo, video, Portugal