Yes. "Temperature inversions" used to be a favorite explanation for UFOs, especially by Menzel. And frankly, it was greatly overused. Superior mirages are only seen over bodies of water (or possibly an extremely flat plain) when a layer of stable warm air overlays cooler air. This is not uncommon in the spring, because air warms up faster than bodies of water. The tell-tale sign of such a mirage is the double horizon, clearly seen in this photo I took of a superior mirage over Lake Michigan in May, 1970. What we see between the two horizons is an image of the water beyond the normal horizon. You can see the distorted image of a distant ship raised up and stretched out. The "Flying Dutchman."
There is a chapter on Optical Mirages in the Condon Report (Section 6, chapter 4). After wading through a whole lot of mathematics, it concludes,
"a superior mirage image is not likely beyond an angular distance of 1 to 2 degrees above the horizon. Hence, mirages appear "low in the sky" and near the horizontal plane of view. An optical image seen near the zenith is not attributable to mirage."
http://files.ncas.org/condon/text/s6chap04.htm
In fact, the estimate of 2 degrees is extremely generous. When I was a student at Northwestern, I had a dorm room looking out on Lake Michigan, and while I saw the double horizon on numerous occasions, I don't think it was ever more than about one degree in elevation, if even that.
Are any UFO reports attributable to mirage conditions? Undoubtedly a few, but it's not a major factor. From time to time observers in extreme southwestern Michigan (near St. Joseph) report seeing strange lights over Lake Michigan. These are almost certainly the lights of Chicago, normally below the horizon but lifted up by a mirage. I remember one evening sitting in my dorm room and using binoculars to watch a distant train moving along the shore of the lake - in a position where normally only water is seen.
