public class Diretor : MonoBehaviour
{
    [SerializeField]
    private GameObject GameOver;
    private aviao1 aviao1;


        private void Start()
    {
        this.aviao1 = GameObject.FindObjectOfType<aviao1>();
    }

    public void FinalizarJogo()
    {
        Time.timeScale = 0;
        this.GameOver.SetActive(true);
    }

    public void ReiniciarJogo()
    {
        this.GameOver.SetActive(false);
          Time.timeScale = 1;
        this.aviao1.Reiniciar();
        this.DestruirObstaculos();

    }

    private void DestruirObstaculos()
    {
        Obstaculo[] obstaculos = GameObject.FindObjectsOfType<Obstaculo>();
        foreach (Obstaculo obstaculo in obstaculos)
        {
            obstaculo.Destruir();
        }
    }
}

ta dando esses erros aqui : 
Assets/scripts/Diretor.cs(34,9): error CS0246: The type or namespace name `Obstaculo' could not be found. Are you missing an assembly reference?

Assets/scripts/Diretor.cs(35,41): error CS0844: A local variable `obstaculos' cannot be used before it is declared. Consider renaming the local variable when it hides the member `Diretor.obstaculos'