Crafts zipping across the sky in Pittsburgh, Pa.

I step out from my job and just happened to look up and saw a formation of about 4-5 crafts zip across the sky sort of like if birds flew by but much higher than birds fly.  The formation looked like a bird migration (diagonal) but I've never seen or heard of birds that glow in the dark.  It appeared as if the one on the rear of the formation started to break from the formation so they slowed down until it realigned and sped right back up.  I watched until I could not see them anymore.  The sighting lasted for about 30-45 seconds.