That sounds great and all to do a scientific study on it, but honestly, it’s hit and miss. I normally see it on the bridge over the river heading north (or south) on my way home from work, but I don’t follow flight traffic or have any intention to do so. I will say that I’ve seen large military aircraft (C-17’s) as well as passenger 737’s both appear to “halt” mid-air. I’ve lived here for almost 10 years, and I’ve seen about 20 circumstances like this. I over exaggerated with the frequencies in my previous post, but I guess it’s not the rare occurrence it once was, and I was all wild about it when I first saw it too. Honestly, I think it has to do with trajectory and velocity of both vehicles in motion. I can’t prove it, but I believe this to be true