Witness Account

At about 11 am in Sebastian Florida, my 18 year old and I were in the backyard talking. I look up and see this white object in the sky. As I keep pointing up asking is my kid also sees what I'm seeing, I thought maybe it was a parachute. The object moved to the right , over a long clean blue patch of sky. As I really focus, it finally presented its self as a cross or very distinct letter t. As it moved across the sky, it stayed upright it the cross/t position. As it started moving towards a cloud it changed shape into a circle. It then disappeared. What is it!?!