When it comes to mathematics, the shortest distance between two points is the straight line connecting them. However, when a plane flies from its origin to its destination, it doesn’t fly in a straight line between the two points, but rather in a curve. Why is that? Isn’t the plane supposed to fly the shortest distance?
According to the aviation news website “Simple Flying,” if you look at the flight routes of planes on a flat map, they are almost always curved or semi-circular. There are several reasons for this, with the two main ones being related to the curvature of the Earth and the jet stream.
Airlines aim for profitability, so when planning the flight routes of their aircraft, they take the route that saves the most time and fuel. For pilots, they would want the flight route to have airports along the way for emergency landings in case of unforeseen circumstances, the more airports along the route, the better.
Ultimately, speed becomes the main factor in determining the flight route of an aircraft. If you ask a student who has taken math classes what the fastest path from point A to point B is, their answer would surely be a straight line.
This may be correct on a two-dimensional map, but the Earth is not flat. You may need to look at a globe to understand the curvature of the Earth better in order to grasp the flight routes.
In three-dimensional space, the shortest route for a plane to fly is a curved path known as a Geodesic. This can be confusing when viewed on a two-dimensional map.
The straight lines on a two-dimensional map do not translate to straight lines in three-dimensional space, which is why the flight route from the origin to the destination appears curved.
Due to the Earth’s rotation on its axis, the middle part, namely the equatorial region, is slightly bulging. Therefore, flying from north to south around the Earth is shorter than circumnavigating the Earth around the equator.
The curvature of the Earth and its additional equatorial width mean that flying distances bending towards the poles are shorter than straight-line flights.
For example, in the two-dimensional map below, the shortest route from the Americas to Europe is the red curved line bending towards the North Pole, not the red straight line.
Another criterion airlines use to determine flight routes is the jet stream. These high-altitude air currents exist near the top of the troposphere. The troposphere is the lowest layer of the Earth’s atmosphere and is where most weather patterns occur.
The boundary between the troposphere and the stratosphere is called the tropopause, and its height fluctuates between 4 to 12 miles (6.4 to 19.3 kilometers) above the Earth’s surface. This fluctuation causes rapid changes in air temperature and pressure, creating wind tunnels with speeds of up to 200 miles per hour (322 kilometers per hour).
Such extreme wind speeds are most common in winter when the temperature difference is greatest, but regular wind speeds of 80 to 140 miles per hour (129 to 225 kilometers per hour) are also common.
Earth has four major jet streams, two in the southern hemisphere and two in the northern hemisphere. Due to the Earth’s rotation, these jet streams mostly flow from west to east. The two most important ones for airlines are the polar jet streams near the Arctic Circle and the subtropical jet streams near the equator.
This means flying along the jet stream can shorten flight time, while flying into a jet stream can slow down the aircraft.
Although flying along the jet stream is a significant advantage, there is a downside called clear air turbulence. Clear air turbulence occurs at the edge of the jet stream and is much more severe than normal turbulence, making it almost unpredictable. This is why it’s essential to fasten your seatbelt when on a plane.
Previously reported by Epoch Times, turbulence is caused by irregular movements of air, leading passengers and flight attendants to experience sudden lateral or vertical vibrations. While turbulence can cause injuries or fatalities, such accidents are very rare, making them less common than other types of transportation accidents such as car crashes, so there is no need to worry excessively.