I was driving north on u.s. 287 about a mile north of springfield colorado when I saw a light appear in the sky about my 2o'clock and about 45 degrees above the horizon it was desending at about 30 degree angle and moving south west, it brightened as it got closer, like an airliner coming in to land from about a mile away, it then began to level off, as it turned to the west, it was so low on the horizon I thought it was a crop duster getting an early start, I then thought no, wrong time of year, at the same time it sped up maintaining level flight until it was out of sight beyond the horizon. I then passed a small airport and thought ok it was private jet or military.about an hour later around lamar colorado I turned on the local am radio station, to my surprise the morning host's remarked how they had seen it too, only it was weird because they said they saw it north of lamar and that other people in Denver reported it north of them and that it was even seen in wyoming, that means what ever I saw that appeared to be a crop duster or small jet maybe a mile or two away must of been very large and very bright, because I was seeing it at least 300 =400 miles away !!! I can't believe that something that bright and big didn't get the attention of the military or other government agencies !! Thank you for your time and for the site. [Name removed/cms/tg]