Why airplanes don't always fly in a straight line

During the 4 years of activity Airlinestravel.ro, I attended and participated in numerous discussions about the flights of airplanes. There are people who wonder why airplanes don't always fly in a straight line. Those who flew the plane, you noticed that the plane does not always fly on a straight path between 2 airports.

As with aviation, there is no single simple answer. EUROCONTROL tries to clarify the puzzled people, offering several reasons why a plane does not always fly straight.

The flight between 2 airports

1. First, the Earth is not flat. Even if we look at two-dimensional maps, we have learned that the Earth is a flattened spheroid; flattened at the poles and flattened at the equator. Under these conditions, the shortest route between 2 points is not a straight line, but a fragment of a very large circle.

Ex. The shortest flight between Paris and Vancouver is over Greenland, although the 2 cities are apparently on the same parallel.

2. Aviation has grown and grown considerably from year to year. The number of flights has also increased greatly, reaching hundreds of thousands of daily flights. In the beginning, the planes were guided by the relief shapes (rivers, valleys, mountains, etc.) and by the ground transportation (roads, railways, etc.).

Then came the radio signals and a whole network of airways was developed and organized in an efficient way.

For the safety of the flight, but also for the good air organization, the planes need to fly through these network nodes, but also by approaching backup airports. Above you have the highways that cross Romania.

3. Weather conditions greatly influence the trajectory of a flight. Even in the air, the shortest road is not always the fastest. Strong winds can greatly slow down an airplane, and this phenomenon can best be seen when crossing the Atlantic Ocean.

Due to the rotational speed of the Earth, strong currents appear in the atmosphere. The best example is Jet Stream, which runs from west to east. The trajectory of a Jet Stream is usually misleading. A jet stream can be stopped, divided into two or more parts, combined into a single stream. The strongest fluxes are polar waves, which are at 9-12 km (30,000-39,000 ft) above sea level.

Such a wind may help the aircraft to fly faster from west to east, but it may slow down if it flies from east to west.

In addition to these air currents, clouds and storms lead to trajectory change. Whoever flew the plane, he could probably see how the pilots changed course to bypass a storm-cloud region. At the same time, pilots seek to bypass even the areas with more severe turbulence.

4. Some commercial and civilian flights may be diverted due to military exercises or closed airspace. Do you remember the case of Boeing 777-200ER Malaysia Airlines (MH17), which collapsed in Ukraine? After that accident, the Ukrainian airspace was closed and the planes had to bypass it.

5. Even if we talk about flights and sky, you know that crowds can occur here, and EUROCONTROL is looking for the most efficient solutions for safe and air-conditioned air traffic.

As you can see, there are many factors that determine the flight path. And no matter how much you want, two airports cannot always be connected by straight-line flights. As exemplified above, not always the straight line flight is also the fastest or most economically efficient.