I see these all the time in early August for a decade now (from Orem). Initial theory was small Perseid meteors breaking up into dusty swarms because of origination in the north sky (Perseid’s radial) generally south(ish) bound and the timing (only see them in early Aug). I note that many seem very high slow moving and some seems closer and fast moving (covering half the visible sky in 8 to 16 seconds). Migrating birds fly 15 to 20 mph only go faster to escape predation. These objects seem much faster although the general line and v formations seen do looks like flock formations. Also it is unusual for most birds to migrate at night and those that do, typically do not do so in flocks, from an admittedly cursory amount of research. Bats fly slower than birds too and not to great heights – so they are doubtful. Especially when you consider that the chaos of a bat swarm doesn’t match the patterns we are seeing. The altitude of this phenomenon is hard to gauge – I’m working on this. I have not seen any news from the SLC or Provo airports warning about increased bird activity either. Lights from the Valley floor may lend credence to the bird theory. Not sure why we wouldn’t see this often in the spring and the fall. August 2 and 3rd there was nothing in the night sky like this. August 8th the sky was alight with them. Whatever they are – they are beautiful!