On the day of the sighting, was outside of the residence doing various yard work chores, and taking a break within a shaded area on the rear deck area of the location. was facing east, and became aware of the sound of multiple jet turbines in the air seemingly to the south, southwest of my position. many commercial airliners pass in close proximity to the location, on "approach" to dia, so began to casually glance in the direction of the noise. as my eyes swept through the sky towards the perceived area of the noise, they locked onto movement noticed at a steep angle above me and a little to the southeast of my position. observed a small, somewhat boomerang-shaped aircraft traveling quickly on a linear southwest-to-northeast trajectory, that appeared to be of a medium-grey coloration over all, similar to the shade used on many military aircraft. as i watched the object's progress, i noticed its size was approx. that of a small fighter jet similar to a f-5, and about the time i realized that the noise from a multiple turbine airliner would not match such a small craft, i noticed that the turbine noise heard did not progress along with the object being observed, instead remaining in a location now to my south. realizing that the noise heard did not seem to originate from the object under observation, i intentionally began to quickly visually scan the underside surface of the object in the attempt to notice any exterior features. its surface appeared to be smooth, with no noticeable exterior features seen from underneath, with the possible exception of a large, circular "hatch" centrally located upon the underside. distance, speed, and sighting duration precluded much examination towards detail, so the underside hatch may not be accurate. speed, altitude, and trajectory appeared to remain constant throughout the observation, and view of the object was lost behind blocking dense tree foliage to the northeast. upon the object being lost from view, i noticed that the jet turbine noise seemed to be coming from a position to my south, southeast and after looking in that direction discovered the source of the noise as a conventional airliner on approach to dia, with a generally west-to-east trajectory. both the object and the airliner appeared to be at an altitude of approx. 8,000-10,000 feet, a little under the prevailing cloud layer in the area, at the time. the object appeared to be traveling at approx. 2x+ the speed of the airliner on "approach speed" to the airport, and no noise was detected associated to the object over the background noise of the airliner's turbines. speed, altitude, and travel directions of the object and airliner would have likely had both crossing paths in close proximity to each other. to best of recollection, the sun was at approx. 60 degrees in the south, cloud cover was altitude "layered" while being heavy but broken, temperature was warm-hot, and very light breeze from undetermined direction. sketch available.