suspending in one place for a longtime square no movement

I noticed something in the air above my lead digger on the job line for approximately 10 minutes it started to get darker and moving around a little bit. Continued to do my job and what I was doing. Every time I spun around on my excavator i saw that it was still there. after a while i grabbed my camera and began to shoot video of it. I thought it was strange because it was in one spot for such a longtime that is why i grabbed my camera and began filming. It stayed there for 31 seconds and the boom of the lead excavator covered the object and then it was gone and there was a dark cloud in its place. Thank You for your time.