At approximately 4:30 PM, Feb. 5,2009, I was standing outside of work, having a smoke, Tinley Park,Il.,noticed an object, very high, heading wsw to ene very fast. It was leaving a very small contrail, about width of my thumb held at arms length. Covered from horizon to horizon in less than a minute. I thought this was a jet, still might be, but as of yet, never saw one so high and going so fast. Flew very straight line, no deviation from speed or path.