6 lights flying in perfect large triangle formation. 2 were flashing orange.I was standing in my backyard, when I noticed a formation of lights moving in perfect unison in the shape of a triangle. There were 2 strobe type lights (1 in the front and the other on the right "side." There was a sound but I didn't hear it until the lights were almost out of sight behind the trees. The sound seemed to travel across the sky at the same speed as the object.