Full Description & Details

Flying from Chicago to Denver on a night flight:

To the North of us I could see the lights of a freighter flight enroute to Portland, Ore.

ATC asked the freighter if they had any traffic in sight. They(the freighter) indicated no visual contact. ATC then asked an aircraft following the freighter if they had any visual contact ahead. The following flight confirmed visual contact with navigation lights of an aircraft ahead of them, but nothing else.

Atc Then stated that the radar return must ba a high altitude military operation.

A few mmoments later Atc asked the freighter to confirm no visual contact, because the ATC radar indicated the contact was flying circiles around the freighter flight.

ATC then reported that the contact proceeded North at very high speed and was gone over the horizon.

Reported Sighting?