Black oblong/rectangular ufo tumbling and turning without gaining much altitudeI was taking some video on my new S7 edge of a rare thunder storm with lightning flashes, which we very rarely get in our city. I noticed something gain altitude in a tumbling fashion out of my peripheral vision and quickly set myself up to record it as steadily as possible resting my arms against the corner of the building for support. The object was sort of oblong, or perhaps even rectangular, and black or very dark in color. I live adjacent to 2 active airstrips, one being the small craft airport Merrill Field, and the other being JBER (Joint Base Elmendorf Richardson), and so I am very familiar with aircraft of ALL SORTS. Everything from single engine Cessnas to AWACS (I've even taken a picture of a Royal Australian type of aircraft very similar to an AWACS but with a "table top" rectangular radar setup as opposed to the circular American style reconnaissance dish, I digress. The object had a very peculiar wobble and tumble to it as it pret! ty much remained on a straight heading moving from N/NE to W. It was unlike any plane, helicopter, drone, balloons or birds that I've ever seen and I am at a loss as to what it was. It IS a UFO in the truest sense of the term, although I can't say with any assurance that it was a "space craft" it is most definitely an enigma. I was able to follow it relatively smoothly for a couple of minutes before it disappeared behind some building and tree in the horizon. Perhaps Merrill Field or JBER may have visual or radar sighting of the object as well...