Strange object over Houston, Texas (midtown) on June 18, 2009

At roughly 10:00PM last night I stepped out onto my 3rd story balcony to have a cigarette.  I happened to look up into the sky as I usually do and noticed an odd shaped object moving from South to North at a fast pace. I wouldn’t be able to give an actual figure as far as it’s height off of the ground mostly because it was a densely dark object. One thing that intrigued me is that it was running silent and had no blinking lights whatsoever.
Also, due to the fact that it was dark, it was fairly invisible in the night sky. The only reason I was able to notice it and distinguish its shape (fairly triangular) was because it flew just under some glowing night-time clouds. It flew right through a known air traffic lane. So soon after it passed the clouds it became invisible once more and then a passenger aircraft flew through the same airspace at approximately the same altitude, which allowed me to guess its size as roughly that of a large truck.
It all happened very fast.  It was a partly cloudy night, so had it not been for the small cloud it passed under I would guess that I wouldn’t have noticed it at all.