During a hike along the powerline trail south of buckley air force base, i stopped to make a cloud and contrail observation for my records. at 12:12 pm on october 3rd, a flashing object flying east to west caught my eye. the object appeared to be flying near but below the same altitude that the visible commercial jets were cruising at, roughly 15,000 to 18,000 feet. this educated guess was based on my observation of altrostratus clouds that were directly above the object. altostratus normally form between 6,500 and 24,000 feet. on that day the cloud cover was above 20,000 feet. i stood in the middle of the trail, completely memorized by the object as the object casually, silently moved overhead. having served in the us navy for 17 years, i dug deep into my memories to see if i could ever recall seeing an object like this. the object continued east to west then after about a minute it flew right over me, heading to a large open-space and landfill to the east. it continued to flash from black to a very strong white light in at a constant rhythm. i glanced at some of the commercial aircraft in the area to determine if they were reflecting light from the sun. none were. once the object reached the end of the runway just south of the air force base, it began conducting maneuvers that would be more consistent with a rotary wing aircraft. it swung back around to the west and continued back to where it came from. it continued to flash but appeared to have some purpose by the way it was hovering, roughly over the superfund site about 2 miles to my east. i thought, "what the heck?" if this thing was a helicopter, how did it get to that altitude, and why did i not hear the beat of its rotors? as i began to reach for my cellphone to notify the authorities, the presidential alert vibrated and rang over my phone at 12:18 pm. i jumped, almost out of my shoes. that was a strange coincidence. i dialed the switchboard at buckley afb and got the desk sergeant for the colorado national guard. i identified myself as a former military officer that served at his base then described the appearance, behavior and location of the object. he asked me if it was seen over on the base-side of the perimeter fence. i told him no but to check his radar between 12:12 and 12:18 pm and that he should see a object to the south east of the base. he asked me if i thought it was a drone. i told him "not at that altitude, not a consumer grade machine." he thanked me and then hung up. i looked back up and tried to find the object again, but it was gone. i called and reported in detail what i had seen to 9 news in denver. the reporter seemed in a hurry and i was under the impression that he did not take down my observation. this object was bizarre. it was not a commercial airplane, a trash bag floating overhead, a hawk or eagle soaring, a weather-balloon or a child's balloon, a meteorite or one of the aircraft from the base. my experience in the military and the years i spent launching and monitoring weather balloons and observing cloud cover tells me that this object needs some explaining. i hope others in the area had made and reported the same observation.