Why Flight Times Are Different When Flying To Same Destination

Take for instance, flying to New York in the United States (US) from Nairobi, Kenya takes longer than the return journey...

Why Flight Times Are Different When Flying To Same Destination
Image of an aircraft in flight. /FILE

If you have been a frequent flyer, you may have noticed that you spend different times travelling from one destination to the next, mostly on direct international flights.

Take for instance, flying to New York in the United States (US) from Nairobi, Kenya takes longer than the return journey (New York to Nairobi). The initial flight takes about 15 hours while the reverse flight is about 13 hours and 30 minutes.

"A plane flying from Egypt to Kenya takes approximately 32min but a plane flying from Kenya to Egypt takes approximately 1 hr 47min, anyone who understands why coz I'm confused anyone??" Twitter user Juddah posed to members of the public.

In a bid to get a response from local aviation experts, Kenyans turned to the one pilot that made headlines owing to her landing skills at Heathrow Airport amid strong winds in February 2022; Kenya Airways (KQ) captain, Ruth Karauri.

Captain Ruth Karauri inside a Boeing 787 aircraft. /STANDARD DIGITAL

She confirmed the difference in flight duration as caused by atmospheric phenomena called “jet streams”. This is also known as the strong westerly winds and is a very high-altitude wind blowing from the west to the east across the Atlantic.

What Are Jet Streams?

When an aeroplane is moving in the same direction as the wind, it will travel faster because it is getting that welcome boost of tailwind. When an aeroplane is travelling opposite the wind direction, however, it will get that drag resulting in a slower travelling speed.

"Lots of people tagging me on this so let me say first of all that there’s no plane that can cover the distance between Kenya and Egypt in 32mins. Average flying time should be 4hrs 50min give or take 20 min depending on aircraft type.

"That said, in some situations where you have very strong winds (jet streams), the flying time to and from a destination can greatly vary. A good example is flights to the far east where during some seasons the flight outbound takes 9hrs and the flight back 7hrs or less," she explained.

According to her, the wind acting as a tailwind in one direction will push the plane to go faster and a headwind when flying in the opposite direction will slow the plane down. Flying at the same indicated airspeed both ways, the effect of the wind either increases or decreases your ground speed.

"The effect of the wind will usually be more noticeable on longer flights. Shorter flights (5hrs flying time or less) will have a variation of probably 20mins i.e 4hrs 30 min outbound and 4hrs 10 min inbound. I hope this helps," she added.

It's like imagining yourself swimming against or towards the current. As long as our planet rotates, the global wind will always travel from west to east, which is determined by how our planet rotates and how much heat it is getting from the sun.

Since the equator gets more sun than any other part, it will always have warmer air rising towards the north or south poles. The warm air goes around the globe from north to south and back again.

Do jet streams cause turbulence?

According to Tripzilla, pilots are often trained to reduce airspeed when the winds are to their advantage to save fuel costs, and also know how to avoid jet streams when it is moving against them.

Jet streams can sometimes cause a bumpy flight when planes get sucked into these forces of nature. They are sometimes unpredictable even when the weather looks calm and clear.

Since jet streams separate hot and cold air and are heavily influenced by air temperature, they are more intense in the winter when the temperature difference between the Arctic and the tropics is the highest.

The jet stream is not a straight pattern of wind, but rather a wavy, snaky one because of the air pushing from the north and south. The mixing of air will cause turbulence when a flight is at the edge of the jet stream and is interacting with slower-moving air.

A window seat view of an aircraft in flight. /FILE

Another determining factor in different flight times is some airlines may choose to fly more direct routes than others which could also lead to differences in travel times. Some airlines may choose to fly longer routes to avoid severe weather conditions while they also have to consider air traffic restrictions, especially in flight plans.

Aircraft performance can vary from plane to plane which could cause one flight on the same route to be faster or slower than another depending on its capabilities.