  The saturation length of aeolian sand transport ($L_s$), characterizing the
distance needed by wind-blown sand to adapt to changes in the wind shear, is
essential for accurate modeling of the morphodynamics of Earth's sandy
landscapes and for explaining the formation and shape of sand dunes. In the
last decade, it has become a widely-accepted hypothesis that $L_s$ is
proportional to the characteristic distance needed by transported particles to
reach the wind speed (the ``drag length''). Here we challenge this hypothesis.
From extensive numerical Discrete Element Method simulations, we find that, for
medium and strong winds, $L_s\propto V_s^2/g$, where $V_s$ is the saturated
value of the average speed of sand particles traveling above the surface and
$g$ the gravitational constant. We show that this proportionality is consistent
with a recent analytical model, in which the drag length is just one of four
similarly important length scales relevant for sand transport saturation.
