If one were to travel from New York to London, it would typically take about 6 hours, but when they travel back from London to New York, it will take a slightly longer. For a frequent flier, they would realize that flying from east to west take slightly longer time than flying from west to east. There is a reason behind that phenomenon, which stems from the rotation of the Earth and the movement of high altitude winds known as jet streams. The Earth rotates from west to east, which would seemingly make sense that traveling from east to west would take less time since one is traveling towards their destination which is equally moving towards them as a result of the Earth's rotation. However, the reality is actually the opposite. It is faster when one travels eastward than traveling westward.
The Difference in Speed Rotation
The Earth is a sphere, and this shape has a significant influence on numerous natural phenomena such as weather conditions, seasons, GPS, and flight times among many others. Since the Earth is a sphere, different regions of the planet rotate at different speeds, and as one moves away from the Equator towards the poles, the rotational velocity decreases. Typically, along the equator one experiences higher rotational velocity because it has to cover a longer distance than other parts of the Earth. The Earth is a solid planet and it rotates on its axis once in about 24 hours and given its spherical shape; it means that the Earth rotates faster at the equator than it does in other locations. The circumference of the Earth at the equator is approximately 24,855 miles, and since it takes 24 hours for the Earth to complete one rotation, the speed at the equator is obtained by dividing the distance by time and therefore giving the speed at the equator at about 1,036 miles per hour. At the latitude of about 40 degrees north, which corresponds to cities such as Ohio, Columbus, and Philadelphia, the circumference of the Earth along this latitude is about 19,014 miles. Dividing it by 24 hours it gives a rotational speed of about 792 miles per hour. While on the North Pole where the distance around the earth is zero, dividing it by 24 hrs would give a speed of zero.
Traveling Eastward or Westward
Taking a flight from New York to London will typically take about six hours, but when flying back from London to New York, it will take significantly longer than 6 hours. This concept is common for all flights traveling from any eastern direction to the west taking longer time compared two flights traveling from any western direction to the east. It was first found out in 1952 when the captain of Pan American World Airways flew non-stop from Tokyo to Honolulu. The direct flight lessened the travel time by 7 hours of the typical travel time. The reason why flights take a shorter time to move from east to west is because of the air currents commonly known as jet streams.
The Jet Streams
Jet streams are air currents of high altitude which are generated by the rotation of the Earth together with the heating of the atmospheric air, and they are typically westerly winds. They are found at the tropopause, which is the border between the stratosphere and troposphere; it is the region where almost all the weather patterns of the Earth take place. The tropopause varies between 6 and 11 miles above the surface of the Earth or an altitude of about 30,000 feet. Jet streams are more pronounced during winter when their speeds could reach above 275 miles per hour, and it is the time when the difference in temperature between the warm and the cold air mass is at its highest. The jet streams are often thousands of miles long but could be some hundred miles in width and a couple of miles in thickness.
How Jet Streams Affect Flights
Any flight through the transatlantic route would vary considerably on time it takes to cover the route. An eastbound flight for instance from North America to Europe would typically take a shorter time compared to the flights moving in the opposite direction and this is as a result of the push factor of the jet stream. A plane flying to the eastern direction from the west is carried along by the flowing jet streams, and as a result, they save on time and fuel, as well. Most pilots are trained to reduce their speed when the winds are in their favor to save on fuel. The North Atlantic jet stream achieves their peak intensity particularly between January and February when the difference in temperatures is highest between the Equator and the North Pole. Flying in the western direction across the Atlantic Ocean particularly from Europe to North America can take a significantly long time especially when the jet stream is at their peak flowing from west to east. For this reason, flights take an unusual route by flying closer to Greenland as opposed to heading directly to the west across the Atlantic Ocean.
The World’s Longest Flight
One of the longest flight routes in the world is from New York to Hong Kong. However, when taking this route, the pilot does not fly direct westward over North America and the Pacific Ocean, but instead, they move due north and curves up over the North Pole then turn down over Russia and China and then finally into Hong Kong. Surprisingly, this is the fastest route, and it shortens the traveling time by about 2 hours. Initially, the airlines have been flying over the Arctic for a long time, and in 1998 the Airlines began using the transpolar route, which has now become common. The route became popular in the 2000s as a result of Russia opening up its airspace together with the liberalization of bilateral agreements, and the increasing demand for international flights from and to China.