I had taken a day off from work on Monday December 2nd. A little after 2 PM I was by my back door and looked out the window. I noticed a persistent vapor trail materializing across the cloudless sky, basically east to west, passing just south of my house. I couldn't see a plane! A long white trail of white material was forming across the sky, as if being emitted by a plane!! I ran and grabbed my camera and got several shots of the phenomenon, the included image the first taken. The sky was slightly hazy, but cloudless. The vapor trail persisted much longer than other planes, all visible (and recorded) passing by which dissipated about 30 lengths behind such planes. This east to west vapor trail persisted hundreds of plane lengths, although, again, no plane nor craft could visually nor photographically be detected.
I recorded this same phenomenon on November 27th, 2010, 4:28 PM, and reported it to MUFON - it can be found with a search. In comparison you would note that the vapor trail appears to be at the same height and traveling in the same direction as this event. Now as then, I report this phenomenon in the strict sense of reporting an unidentified flying object. I also report this as circumstantial evidence that an "invisible" craft is ejecting material into the air over St. Louis on some soft of regular basis. Each time I happened to witness and record these events by chance, where, statistically, this event must be happening in a much shorter periodic time period than every 3 years, as if one time wouldn't be enough to be disconcerting :)