Triangular fire balls in August evening sky

My brother and I were following my parents home from a church ice cream social on a Sunday afternoon in August of 1977. While traveling north on the Saint Marie road just outside of Olney, my brother and I noticed three bright orange fireballs in a triangular pattern moving up and down extremely rapidly in a zig zag pattern. The fire balls stayed together in the triangular pattern at all times. They were no more than 1/4 mile west of us, moving at least 500 feet up and down within a second or two.
 We contacted our parents on our CB radio to ask them if they were watching what we were. They were watching it, too. Within a minute, the triangular fire balls dipped one last time behind a grove of trees and disappeared. My brother and I drove to where it disappeared, but there was nothing there.
Date is approximate; witness elects to remain totally anonymous.  PD