Ball or round object very high about 25000 feet following Passenger jets.

Two passenger aircraft were flying the same route at different elevations. The one headed over Nashville Airport to the Northwest had a small ball or round object following it, then as the higher aircraft approached the point of crossing the path of the plane headed NW, the ball stopped and went west some small distance off the contrails and waited for the plane headed southeast to pass, then after it had passed what appeared a small distance beyond the round object the round object went back to the contrail and approached the back of the plane headed southeast and followed it very close until it faded in the distance beyond visual site.