I was working on a rock crusher at the time of this event. I was facing west with the sun behind my back. The crusher had not yet been fired up so there was no noise from the machinery and the only noise was coming from the highway and even that was just the sound of distant passing cars. I looked up as I heard the sound of a low flying jet and saw a jet liner that must have been coming out of Casper. It was only a thousand feet or so up as I could make out the piping on the plane ( red - must have been a WESTERN flight) and I could even make out the individual windows. I have seen a few flights come out of Casper at around that altitude. As the Airliner continued to move ( it was going on a SE course - I assumed toward Denver) Another object appeared below and to the rear of the Airliner. At first I thought that it must be some sort of Towed blimp. My logic for that was that It was a seamless craft and obviously made of Metal ...it was glinting in the sunlight as did some of the parts of the Airliner. This object made NO noise ( the Airliner did) This object had no identifiable doors or windows and it appeared to be about 3/4 of the length of the airliner it was following. It was only slightly thinner than the Airliner. After the first minute or so of watching the event before me I discarded the idea that the object was a blimp..or even another aircraft. It was following the Airliner maybe 500 feet below.. and 500 feet behind.. It moved in perfect unison with the jet as though it was tethered by a iron bar. Where as I could clearly make out the details of the Airliner ( Wings- piping-windows- noise) the object had none of these. It appeared to be a metal cigar shaped craft with (No windows - No Doors or seams - No paint or logo - No Wings or Engines- and No noise). The Airliner and the object continued past my position and flew directly across two roadways..Ther first a minor two lane highway and then another mile and a half further it crossed the I-25 interstate and kept going till it was beyond the horizon and my ability to observe it further.The entire sighting lasted perhaps 4 minutes. I have since then had a few sightings of things I could not identify flying through our skies but nothing that compares in detail to this sighting.