Earth's rotation doesn't help airplanes much: the air is almost stationary with respect to the earth and airplanes move relative to the air. Suppose a hot air balloon. Air is dragged along with the rotation of earth, so the balloon will almost be stationary. (Ok, it moves, but only slowly.) So whether the plane travels east or west for 1000 km, it has to travel 1000 km against air which is 900 km/h slower.
There is a meteorological effect that planes can use, though. The jet stream is a channel of very high speed winds at high altitude.
Planes traveling east, for instance from the US west coast to the east coast, or from America to Europe, take advantage of this jet stream to save fuel. Note that the jet stream isn't anywhere as fast as the earth's rotation. At 50 degrees north the earth's rotation is about 1000 km/h, while the jet stream is about 200 km/h.
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