Aircraft speed is added to earth rotational speed when flying to the east, centrifugal force is increased compared to a westward flight. That means the aircraft weight is reduced = smaller lift, means flight with lower AoA = lower induced drag.
Can this in reality be used for less drag and greater speed or better fuel consumption?
If a plane flies east with speed of 1666km/h, centrifugal acceleration is 0.134m/s2, that means it has 1.37% less weight. If the plane weighs 78700 kg then the reduction in weight is 1078kg, when flying east!
If a plane flies westward at 1666km/h (same as earth's rotational speed) then looking from space (inertial frame) plane looks stationary, so centripetal force = zero.
This is the Eötvös effect: