Unfortunately for UFO researchers, the three antenna on each satellite are highly reflective. like giant mirrors in space, they reflect sunlight to observers on the ground and occasionally flare brighter than the planet Venus, You may sometimes even see them in daylight.
from the ground, an Iridium satellite produces a flare lasting up to 20
At its peak intensity - which can last for around 5 seconds - the flare can be as bright as magnitude -7 (Venus is - 4). Then it will fade and be lost to the naked eye.