Low flying string of white lights 12000 to 15000 feet heading west to east. Witnessed for 10-12 seconds then faded and disappeared

We witnessed a string of low flying bright white lights 15-18 of them at low altitudes for 10-12 seconds moving from the west to east direction at 9:45 pm on a clear flawless night. Once they were in front of us just above tree top angle approximately 12-15000’ they all vanished on after another. These were not Starlink satellites. They were to low and they vanished like some type of cloaking device was activated. If they were satellites we could have watched them travel to the eastern sky.
We took pictures and a video of them but they did not record to the cell phone. No images appeared on the phone’s camera.
No sound was heard. No other aircraft in the area. Crafts we’re heading in the direction of Ellsworth Airforce Base outside do Rapid City SD.