Neglect the centrifugal acceleration, which is of order , and use the local flat-surface approximation. To zeroth order in , the height above and flight time are
Inserting this vertical velocity into the Coriolis acceleration gives the eastward component
With , two integrations yield
to first order. Horizontal velocity is already of order , so its effect on vertical acceleration is of order . Thus the flight time remains at this order. The Coriolis deflection of a vertical projectile at landing is
The displacement is westward, and its magnitude is . The horizontal speed remains westward during the flight: . This explains why the eastward acceleration on descent does not cancel the earlier displacement.