What it’s like to fly on the world’s most turbulent route

Daftar Isi

Before it dissipated on 27 January. One occasion saw a British Airways flight from Las Vegas to Heathrow reach a speed of 814mph on 22 January, thanks to Atlantic tailwinds that brought it in about 45 minutes ahead of schedule, accompanied by sudden bursts of turbulence.

At a par with the worst to be found in the world.

To achieve that, you need something that this nation notably lacks: high mountains.

Made by self-proclaimed "weather enthusiast" Ignacio Gallego-Marcos – a Spanish expert in computational mechanics, who is now based in Sweden – this engaging online database runs the numbers to calculate the flight routes that are most at risk of turbulence. As a phenomenon, Gallego-Marcos suggests – to a certain extent – turbulence is predictable. And the statistics he has compiled point to one area in particular; namely, the bottom of South America.

Six flights involving take-offs or landings in the Chilean capital Santiago, or the Argentinian cities of Salta or Mendoza, made last year's list of airports most affected by turbulence. These three cities were also at the top of the rankings for turbulent airports in 2022. When measured by the turbulence-intensity metric EDR (Eddy Dissipation Rate), Santiago leads the figures, with an average EDR of 23.065. Mendoza came second, with an average EDR of 22.765; Salta came in third, with an average EDR of 20.407. The most turbulent flight of the past 12 months was a flight from Mendoza to Santiago, which had an average EDR of 24.684. You would have assumed the seatbelts were on.

Turbli categorises its turbulence ratings into five categories for EDR: Light (0-20); Moderate (20-40); Strong (40-60); Severe (60-80); Extreme (80-100). While Santiago et al fall into the "moderate" category, Gallego-Marcos comments that "the ranking tables are yearly averages."

The Andes Mountains' snow-capped crest stretches for 5,530 miles, unbroken, all the way from Columbia and Venezuela in the north of the continent to Chile and Argentina at the base. The highest peak within this chain is found in Argentina; Aconcagua towers above at 6,961m (22,838ft). On average, the Andes ridge reaches a height of 4,000m (13,123ft) throughout its entire length.

In other words, it's a considerable physical obstacle. And although commercial planes certainly fly above it at much higher altitudes, they're not immune to the atmospheric effects of crossing it. Particularly if they're flying to Santiago, which is so close to the Andes that its eastern horizon is dominated by them, or to Mendoza, which is a mere 140 miles away from its Chilean neighbour, but crucially, on the opposite side of the ridge. Salta is located further north, where the Argentine province of the same name meets Bolivia and Paraguay, but it goes about its business (winemaking, to picturesque result) on the ridge's lower slopes.

An explanation as to why a tremendous rock formation creates turbulence could form the basis of a doctorate dissertation. However, the straightforward answer is "lee waves" – the phenomenon whereby air currents are pushed upwards and over a significant obstruction in their route. There are further factors to consider, including changes in atmospheric pressure, temperature, cloud levels, and the amount of moisture in the air – but the fundamental theory is that wind flowing towards a series of elevated areas will need to find a way over them. And the higher the peaks are, the greater the waves will be; in some cases, lee waves have been known to reach an altitude of 19 miles (30km). As a result, planes flying over the top can expect to be affected by currents surging upwards from beneath, then pulled towards the ground by the down-drafts that inevitably follow.

The plane you're strapped into at 36,000 feet is now bucking and jolting, it doesn't exactly calm the knot of anxiety you feel in your stomach as the aircraft shakes severely in a sudden, stomach-churning motion. I can describe this having had personal experience.

Over the course of 20 years as a travel writer, I've flown between Chile's and Argentina's airspace on three separate occasions. I still clearly remember the first time, when I was approaching Santiago: the Andes, with their pale winter beauty, coming into view beneath the aircraft. Then, without warning, the plane lurched and rolled as if it were a washing machine and I was a load of dirty washing. It felt – in my state of anxious terror – as if this unsettling experience dragged on for an eternity. In reality, it was no longer than a couple of minutes. It gave me a lasting impression of what I could expect on future flights over the Andes – but advance warning didn't reduce my anxiety on my second and third crossings.

Of course, the Andes are not the only mountains whose turbulent conditions affect aircraft movements. Among the ten most turbulent flights identified by Turbli for 2024, three took place in the Nepalese capital Kathmandu or the Tibetan city Lhasa – majestic strongholds of the Himalayas, situated at 4,600 feet and 11,995 feet above sea level respectively. This phenomenon is seen on a global scale, with Kathmandu-Lhasa identified as the most turbulent Asian flight last year, boasting an 18.817 EDR rating. Similarly, mountainous conditions impacted flights in the USA, with the 349-mile route between Albuquerque in New Mexico and Denver in Colorado recording the highest turbulence at 17.751 EDR.

In South Africa, the crown swayed on the Johannesburg-Durban route, over the Drakensberg Mountains (15.064 km EDR). And even relatively flat Australasia was also involved, with the 306-kilometre air-route between the New Zealand cities of Christchurch and Wellington, whose flirting with the Southern Alps resulted in an average EDR of 14.460.

For Europe – all turbulent flight routes culminated in one mountainous region. Each of Turbli’s European top 10 for 2024 took off from or landed at or near the Alps, with the airports of Zurich, Lyon, Basel, Milan and Venice all featuring on the list, and the 298-kilometre Franco-Swiss journey between Nice and Geneva casting a long shadow with an average EDR of 16.065. Remember this, the next time your approach to Heathrow is bumpy…

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