If you’ve ever taken a flight and watched the flight path on the screen on the back of the seat in front of you, you might have noticed that the flight path was curved instead of straight.

But why is this?

Flight paths are curved due to the earth’s surface, with a curved flight path providing the most direct route to a flight’s destination.

Curved flight paths are also practical because they take advantage of powerful jet streams, which make flights faster.

A plane’s flight path is approved by Air Traffic Control (ATC), and the ATC may change the flight path for security reasons, though ATC will primarily change a flight path if there’s high traffic or bad weather conditions in an area. 

Why Are Flight Paths Curved?

Airplanes fly on a curved path to reach their destinations more quickly, since curved paths account for the earth’s surface.

Airlines use the quickest paths because they reduce travel costs and free more time for additional flights. Of course, passengers want to get to their destination as quickly as possible, too.

Curve flight paths look confusing on 2D maps, so they’re calculated using the Great Circle Route, which is also used in sailing. 

Why Planes Don’t Fly in a Straight Line

The earth bulges out slightly at the equator because it revolves on its axis.

As a result, the fastest path between two points is curving towards the pole instead of flying in a straight line.

So, the earth’s curvature makes flying in a straight line impractical due to the greater time it takes to reach destinations. 

Additionally, jet streams also impact airplane flight paths.

The jet streams are a series of winds that help planes fly faster, with aircraft flying in circular paths to take full advantage of them.

It’s therefore impractical to fly in a straight line. 

How Flight Paths Work

  • A plane’s flight path is mapped before taking off.
  • An airline dispatcher uses a computer to analyze the weather and winds between the origin and destination and plan a flight route.
  • The airline dispatcher’s priority is to choose a path that minimizes flight time and exposure to bad weather. 
  • Next, Air Traffic Control reviews the flight plan and modifies it if needed to reduce air traffic.
  • Following Air Traffic Control’s approval, the plane flies the intended flight path.
  • Airplanes also use tracks made of predetermined sets of latitude and longitude coordinates to ensure they’re following the right flight path. 

What Affects a Plane’s Flight Path?

The following 3 factors have the most impact on a plane’s flight path. 

1. Air Traffic

The Federal Aviation Authority (FAA) states that there are as many as 5,400 aircraft in the sky at peak operational times, and separate airspace into multiple corridors to ensure safe air travel.

They’ll inform airline pilots to change flight paths to maintain safety if the airspace gets too crowded. 

2. Jet Streams and Winds

The jet streams, and other powerful winds, usually blow from west to east.

These winds help planes fly faster towards the east, but they can also delay planes traveling to the west.

Pilots change flight paths if the jet streams are too fast for the plane to withstand safely. 

3. Airplane Size

The larger a plane is, the more engines it has.

Having more engines means that a plane can fly for longer distances without needing airports for emergency landings.

Two-engine aircraft especially need to remain close to airports for potential emergency landings. 

As a result, smaller planes follow different flight paths than larger ones.

Larger planes can use flight paths over terrain with fewer airports. But, smaller airplanes use flight paths with more, smaller airports along the way. 

Airplanes Don’t Always Fly the Most Direct Route

Airplanes don’t always fly the most direct routes due to safety reasons.

While the most direct route is the shortest and fastest one, it may not be the safest.

For example, a pilot won’t be allowed to fly the most direct route to a destination if there’s a large amount of traffic on the flight path along the way. 

Flight Paths Can Change Mid-Flight

Flight plans can be changed mid-flight, subject to ATC approval, for multiple reasons.

Flight paths are most often changed mid-flight due to weather and traffic reasons.

Weirdest Flight Paths in the World

Most of the world’s weirdest flight paths are caused by either geographical or political issues.

For example, the Taipei Zhongshan to Xiamen Gaoqi route is used by planes because of the political tension between China and Taiwan. 

Recently, the Russo-Ukrainian war saw a ban of Russian flights from other European airspace and prevented planes from many European countries from flying over Russian airspace, causing great inconvenience. 

For instance, Japan Airlines JL43 normally flies over Russia while traveling from Tokyo to London.

Due to the Russo-Ukrainian war, the flight instead flies over the Pacific Ocean and over Alaska before crossing the Atlantic to reach London.

This flight increased by 3 hours as a result. 

In conclusion:

  • Planes fly curved flight paths because they’re most practical
  • Curved flight paths ensure that planes fly the most direct route and take full advantage of the jet streams.
  • In contrast, direct flight paths are impractical because they would avoid the jet streams and ignore the earth’s curved surface.
  • A plane’s flight path is approved by the ATC beforehand, and it can be changed mid-flight, too.
  • A plane’s flight path is usually changed because of weather and traffic.
  • Planes don’t fly the most direct path to their destination if there is high traffic or another safety concern.

Ella Dunham, a Freelance Travel Journalist and Marketing Manager, boasts an impressive career spanning eight years in the travel and tourism sectors.

Honored as one of "30 Under 30" by TTG Media (the world’s very first weekly travel trade newspaper), a "Tour Operator Travel Guru" and "Legend Award" winner, Ella is also a Fellow of the Institute of Travel, a Member of the Association of Women Travel Executives, has completed over 250 travel modules, and hosts travel-focused segments on national radio shows where she provides insights on travel regulations and destinations.

Ella has visited over 40 countries (with 10 more planned this year).