6 chevron shaped objects seen in the daytime sky doing "loop-de-loops" at high altitude

I was around 15 years old at the time (very good eye vision at the time too), and was riding my dirt bike. I stopped on a hill by the town's water tower to take a look at the town below. It was a clear day, with a brilliant blue sky.
I glanzed upward and noticed what i thought were birds flying in single file. I did a double take, and realized these objects were manufactured, but were following each other in "loop-de-loop" motions. 
They were confined to a small area of the sky (about 80 degrees from horizon in NE sky). 6 of them were triangle in shape and took on the appearance  of silver, kind of like a Jet at a high altitude on a cold day.  
As they did a loop , they disappeared out of sight.I could only figure they were going in & out of our atmosphere.  Only did this for a minute or two , then they vanished.
Witness indicates that the date of the sighting is approximate.  PD