UFO in the sky with flashing lights?

My friends and I were out really early this morning looking at stars and we saw what looked like a moving star. We assumed it was just a satellite but then it's light got really really bright for about 5 seconds and then dimmed after that to almost nothing but kept moving across the sky. Does anyone know what it was? I've never heard of a satellite doing that and it didn't have a tail following it so I don't think it was meteor or anything like that.