problems with Billboard

[NirAbel]

hi,
i'm using Billboard & BillboardCollection to input planes to the map (using Viewer).
i have problem with the altitude of the planes when i'm enter Cartesian3.fromDegrees(long, lat, 0)
i want to see the plane in this position on the ground (altitude 0, but i see him in space!)

this is my code:

<Billboard
color={Color.YELLOW}
position={Cartesian3.fromDegrees(this.state.lng, this.state.lat, 0.0)}
image={image}
scale={0.4}
/>

thank you,
Nir