News

Ever Wondered Why It Takes Longer to Fly from Brisbane to Perth Than the Other Way? Here’s the Surprising Reason!

There is a good reason why you might feel more travel-weary, with additional body aches and pains, when flying across the Australian continent from east to west, compared to west to east. This has a lot to do with the wind direction and wind speed at the cruising altitude of commercial airlines.

The typical cruising altitude for commercial jet aircraft is between 28,000 and 34,000 feet (8.5 km to 10.5 km), which improves fuel economy through lowering fuel consumption in jet engines. At this altitude, flights enter the upper troposphere, which harbours regions of strong winds.

Let's take a closer look at the wind patterns in the upper levels of the troposphere, particularly the band of very strong winds known as the Jetstream.

The Jetstream is a region of higher-speed winds that flow predominantly from west to east. An analogy would be "a river of strong winds", where wind speeds commonly exceed 100 km/h. In certain situations, a narrow band of stronger winds within the Jetstream can reach speeds exceeding 200 km/h.

During the winter months, winds within the Jetstream are typically at their strongest. It is quite common for wind speeds to exceed 140 km/h, and in some cases, they can reach 200 km/h or more.

One scenario where flight times would be extended for westbound flights due to strong headwinds occurred on July 19th, 2024. A powerful Jetstream developed across the southern mainland of Australia, with wind speeds exceeding 300 km/h over southern Western Australia and the Great Australian Bight. For flights traveling to Perth from Brisbane, Sydney, or Melbourne, headwinds exceeding 200 km/h would have caused noticeable delays and increased flight times, while passengers experienced longer durations in the air before reaching their destination.

Image: Forecast winds for 30,000ft on July 19th 2024 with annotated wind speeds exceeding 200km/h bounded by the white line and speeds exceeding 300 km/h bounded by the red line and the axis of the Jetstream marked by the green arrows. Yellow numbers are wind speed in km/h. The line linking Brisbane to Perth shows the shortest distance between the two cities. [Source – Ventusky – ECMWF weather model]

By comparison, during the summer months, the Jetstream generally has slower wind speeds and a lower maximum wind speed. Its location is also more transient, meandering between central areas of Australia and higher latitudes to the south. As a result, the impact on westbound flight times is likely to be less significant compared to winter flights.

The image below shows the Jetstream winds for November 3rd, 2024. The Jetstream is fragmented, with one section located over southern Western Australia and another off the east coast of Queensland. Compared to the winter weather pattern on July 19, any flight delays caused by headwinds would likely be much less noticeable on 3rd November.

Image: Forecast winds for 30,000ft on November 3rd, 2024 with annotated wind speeds exceeding 200km/h bounded by the white line and the axis of the two Jetstream marked by the green arrows. Yellow numbers are wind speed in km/h. The line linking Brisbane to Perth shows the shortest distance between the two cities. [Source – Ventusky – ECMWF weather model]

When scheduling future flights, the airlines factor in variations to flight times due to headwinds and tailwinds on standard flight paths using climatology and weather forecast modelling.

Inspecting the flight schedules for major Australian airlines flying from Brisbane to Perth, flight times in winter average between 5 hours 30 minutes and 6 hours in duration from Brisbane to Perth, compared to summer flight durations of 4 hours 15 minutes to 4 hours 30 minutes.

Scheduled flight times from Perth to Brisbane are normally 4 hour and 15 minutes to 4 hours and 30 minutes all year round, and is similar to westbound flight times in summer.

The Jetstream also has a strong influence on the weather patterns observed in the lower atmosphere and near the Earth's surface. Ben Domensino wrote a story about a severe weather event over southeast Australia in November 2022, which was strongly influenced by the Jetstream. Read the full article here.

Title image: Cirrostratus cloud with a jet airliner contrail in the foreground  credit - unsettled photography