It's a lens flare. It brightens and dims in response to the brightens of AF2's spotlight. It remains in direct line with the spotlight and shifts position as the spotlight moves. At one point it passes through the monument. It "darts off" when the helicopter begins to land and the spotlight shifts right and up. It is a direct line of sight with the spotlight and has a second minor flare between it and the source light that behaves in the exact same manner.