On Sunday afternoon (March 15, 2015) at approximately 5:30 PM I was on my back deck grilling a couple of steaks for supper. A couple of flocks of cranes were flying over headed North. As I was watching them I noticed a passenger plane headed South. This plane must have departed Louisville, Ky. as it was not extremely high in the sky. The sun was low in the west and sunlight was being reflected from the plane. The reflected sunlight was what caught my attention. While watching the plane, I noticed a round silvery object to the planes left side. This object was keeping pace with the plane. The plane started making a slow turn toward the Southeast and the object made the same turn. As the plane was going almost directly overhead the object went from the planes left side, crossing under it and then went above the plane on the planes right side. There is a knob directly in front of my home and I watched until the plane and the object disappeared from view over the knob.The size of the object could be compared to the size of a pea at arm's length. The color was what I would call silver transparent. The plane was not leaving a contrail.