I saw something similar to the 9/11/2011 Michigan objects this past week.
On Monday night (8/20) I was walking west of downtown in Coralville, Iowa. At about 10:50 p.m. I turned around and saw 3 balls of orange fire to my east, maybe a 60-degree angle above the horizon. They weaved a bit, then created & maintained a spearhead formation as they moved from roughly north-northwest to south-southeast at a constant & uniform speed & direction. I think they were higher than local small-planes but lower than transcontinental jetliners. They were too high up for me to see the objects themselves in the dark sky or to hear them (although I later heard a jet-like noise of normal volume that could have been caused by something else).
I could only see the light they created, which was _definitely_ flame: it had the right orange color, it came from an area instead of a single point, and it flickered. After some time, the flames died out one by one. I lost track of the first two objects as their flames faded out, but the last was visible by its faint glow for some time afterward as it continued almost to the southern horizon. The flames had no tails, changes of color, or objects breaking off, so this wasn't heat from re-entry (for meteorites, satellites, or alien spacecraft).
We don't have any military bases nearby, so I have never seen anything like it. My initial guess was that these were Air Force planes on a night training mission, and the flames were either afterburners or a visual aid (perhaps to keep track of where each other were to avoid collisions just while they formed up, before practicing flying in formation at night across the country). However, if the 9/11/2011 Michigan objects were "just above the tree-tops", then perhaps they were balloons that someone released, and they took a bit before settling into formation and drifting with the wind. (I didn't think to check the wind direction that evening, but it was a calm night. I think it was clear, but I forget.) The flames seemed more horizontal than vertical to me, but then I was biased by thoughts of aircraft.