Formation of 15-20 metallic star like objects heading north

I was sitting outside doing my photography for my and looked towards the left facing the west coast of Florida and saw a group of what seemed to be 15-20 metallic objects in a close formation from a distance, at first I thought it was a flock of birds but they appeared for about five seconds coming from a southernly direction then disappeared. The altitude was above the tree line and I wanted to say the altitude was between 15,000 - 20,000 feet. The approach path for aircraft descending into Tampa International is 2,500 -10,000 on the approach path here.