Could you tell me which one is right?

(1) The Earth's rotation has no DIRECT effect on flight time since the air moves with the earth.

(2) Travelling from East to West the airplane will reach its airport sooner.

-Selina

Hi there,

I know that when I go to the United States from Europe that the flight time is different depending on which way you are going. I always assumed this was due to the prevailing winds.

The atmosphere, obviously, rotates with the earth, otherwise you would have supersonic winds near the equator (460 m/s).

The difference in flight time from the U.S. to Europe and back is due to the jet stream, a strong upper wind which travels from west to east and separates the warm air in the south from the cold air in the north. The upper jet stream has winds between 100 - 200 knots (1.943 knots = 1 m/s). On easterly flights, pilots enter that jet stream (route further north), whereas on westerly flights they avoid it (route further south). For example, a flight from Miami, Florida to Frankfurt, Germany (I have traveled that route many times) is always an hour shorter than the return trip. Occassionaly, the difference in flight time is nearly two hours.

By the way, the idea of a jet separating warm air from cold air is used in some department stores during the winter. By blowing air from top to bottom near the entrance, the warm air is kept inside when people come in and out of doors. Cold drafts inside are thus avoided.

Correction: Top wind speeds are closer to 100 knots.

So, the air rotates with the earth's rpm ? Even the air which is far above (near or outside of the boundary of atmosphere) the earth?

-Selina

Since the earth has been spinning for millions of years, I would say that any initial transients have died out by now. Neglecting winds and weather, which are due to the uneven heating of the planet, yes, you can consider the atmosphere to be in rigid body rotation, even at its outer boundaries.