by Strong winds over the Atlantic pushed commercial flights close to breaking speeds at the weekend, with some passenger planes recording ground speeds in excess of 800 miles per hour. Eastbound aircraft, including a Virgin Atlantic flight from Washington DC to London, landed much earlier than expected due to the freak weather.
According to the tracking site FlightAware, the Virgin Atlantic service, on a Boeing 787 Dreamliner, reached a top ground speed of 802 miles per hour at 33,000 feet – about 200 mph faster than average. Instead of taking the usual seven hours, the journey took just six hours and 20 minutes, allowing passengers to land 45 minutes earlier than expected.
Did Virgo break the sound barrier?
The top speed of flight was faster than the speed of sound, which is 761 mph at static sea level conditions. The speed of sound, however, varies with temperature, as well as the medium through which a sound wave is propagating.
Because the plane was traveling in 200 mph winds, therefore, its airspeed was closer to 600 mph, not 800 mph – lower than the speed of sound compared to its environment.
When an aircraft is flying above 25,000 feet, its speed is referred to as Mach number: a percentage of the speed of sound. An aircraft breaks the sound barrier at Mach 1, creating pressure waves that follow the aircraft. A sonic boom is heard when these waves pass over an observer.
Pilots, in general, are not about reaching the speed of sound – which can be dangerous in some cases. Nick Eades, one of the longest-serving Boeing 747 pilots, notes that commercial airplanes are not usually engineered to fly that fast.
“In the early days of jet aircraft, there was a phenomenon called the Mach Tuck,” he says. “As the aircraft reached the speed of sound, the force would push the nose down, which is very dangerous.
“It’s now designed out of the modern jetliner, but still – you don’t want to go near the speed of sound because that’s not what airplanes are supposed to do.”
Virgin’s flight was the fastest civilian transatlantic crossing ever – that record is held by BA and Concorde, which flew from New York to London in two hours 52 minutes and 59 seconds in 1996 – hitting top speed 1,350 mph. In 2020, another BA flight reached speeds of 825 mph – the fastest ever for a subsonic flight – aided in part by a powerful jet stream. The flight took just four hours and 56 minutes.
Power the jet stream
Although the Virgin flight did not win this record, it demonstrated the power of the jet stream, which pilots use to reduce flight time and fuel consumption. This band of fast-moving winds is found between five and seven miles high in the atmosphere, created by heat spreading from the equator to the poles. About 10 miles wide and 2,000 feet deep, westerly winds, in the northern hemisphere, become stronger as altitude increases.
Manoj Joshi, professor of climate dynamics at the University of East Anglia, explains: “The jet stream is usually strongest in winter because of the temperature difference between the equator and the North Pole. There is little variation between times of day, but the jet stream changes as atmospheric waves and weather systems move along it.”
Thanks to climate change, the jet stream is expected to become stronger in the coming years. Near the earth’s surface, the polar regions are warming more than the subtropics, weakening the winds at lower levels. At higher altitudes, however, the opposite is true: the subtropics are warming, and the polar regions are colder, which reverses the earth’s rotation.
For passengers, this means journey times in the Northern Hemisphere are faster when traveling east. “I flew from Boston to London in less than five hours because we had this huge wing wind pushing us,” says Eades. “But if I were to fly from London to Boston, it would take me closer to eight hours because I’m flying into that jet stream.”
Pilots use Met Office data to calculate the potential impact of the jet stream on a journey, as well as the potential reduction in fuel use. A 2021 University of Reading report found that flights between London and New York could use 16 percent less fuel by accurately following jet stream tailwinds. The report also notes that this practice, when done correctly, is far more cost-effective than other measures to reduce emissions.
Jet stream safety
It is unlikely that a passenger would be able to notice the difference in speed until they soon touch down. What they may encounter, however, is turbulence as a plane approaches the edge of the weather pattern.
That, according to Eades, is where the danger lies. “As a pilot, you have to be very careful going in and out of the jet stream,” he says. “It can be a big difference in temperature and speed.”
That jolt is known as clear air turbulence, which can seriously disrupt the cabin and is much more difficult to predict than turbulence from storm systems or cloud cover. “It’s really important to put on the seat belt signs and buckle up, because sometimes you know you’re in an area where there’s obvious turbulence, but it’s not exactly located,” says Eades.
Regardless of the risk of turbulence, the jet stream remains a critical tool in flight path management. As speed increases, will airlines use it even more often? The answer is complicated. Cathie Wells, a research fellow at the Walker Institute, notes that new routing structures, introduced in 2022, are allowing airlines to use the jet stream more easily than before. This means that minimizing time is a priority – for now.
“Air speed is also a key component in reducing fuel use and emissions,” she says. As the cost of fuel increases – and the prospect of reducing carbon emissions – planes may lower their speed while flying jet stream-optimized routes. That means transatlantic passengers shouldn’t always expect to get home as early as passengers on a Virgin flight.
