Jet stream powers flights to 800 mph — but not the sound barrier

On Saturday night, a Virgin Atlantic aircraft took off from Washington, D.C.'s Dulles International Airport (IAD) at 10:45, bound for London’s Heathrow Airport (LHR).

A short time into the flight, as the Boeing 787 Dreamliner climbed to more than 33,000 feet above the New York City area, it reached what appeared — at first glance — to be a fairly notable milestone: a ground speed of 802 miles per hour, according to data from FlightAware.

For comparison, the speed of sound is around 760 mph, per NASA.

That aircraft wasn’t alone.

Also on Saturday night, a British Airways Boeing 777 bound for London reached ground speeds of 812 mph some 34,000 feet above New Jersey. And an American Airlines 777 out of Raleigh-Durham International Airport (RDU) reached 785 mph a night later, also en route to an early arrival at Heathrow.

Don’t worry: You didn’t miss the sonic boom: There wasn’t one.

Can commercial planes fly at the speed of sound?

These jets didn’t actually break the sound barrier over the weekend. They just got a significant push from Mother Nature.

Around the same time those flights took off, the National Weather Service in the Washington, D.C., region noted an unusually powerful jet stream over the mid-Atlantic.

Thanks to where that fast-moving current of air was located over the weekend, it directly affected flight operations.

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“Think of it as a river of air at a high altitude,” said Dan DePodwin, director of forecasting operations at AccuWeather. “Over the weekend ... it was very well aligned with the typical routes planes fly when they go from the East Coast over to Europe, and because of that, there was a significant tail wind.”

In fact, the weather service said, weather balloons detected the second-strongest jet stream dating back to the mid-20th century, with winds as fast as 265 mph at 34,000 to 35,000 feet.

“For those flying eastbound ... there will be quite a tail wind,” the NWS said in a post on social media.

That certainly proved true.

The Virgin Atlantic flight got to Heathrow 45 minutes early, in six hours and 40 minutes. Numerous other flights touched down in London a half-hour early or more over the weekend.

But despite the impressive ground speed readings (not to mention the short travel times to Europe), none of these jets technically passed the sound barrier.

Nothing like the Concorde

Unlike the Concorde, which could legitimately break the sound barrier with flight speeds of more than 1,300 mph as it whisked passengers across the Atlantic to Europe in its heyday, the Virgin Dreamliner wasn’t actually propelling itself through the air at an airspeed of 800-plus mph.

In fact, its actual airspeed — the speed of the plane relative to the air immediately surrounding it — would have been a couple hundred miles per hour slower.

But thanks to the strong winds, its ground speed, or how fast the jet was moving relative to the ground, reached those head-turning readings.

Though Saturday night’s jet stream was especially powerful, the phenomenon is relatively common in aviation — particularly during the cooler months of the year in the northern hemisphere.

"Generally speaking, in January through March, we tend to see stronger jet streams. However, with climate change, that can vary," said Dan Bubb, a former airline pilot who serves on the faculty at the University of Nevada, Las Vegas.

It can be great news for planes flying with the wind, speeding up travel times and helping airlines save on fuel costs.

"Conversely, when airplanes are flying from east to west, they are flying into the jet stream, which will take longer to get to their destinations," Bubb said.

That also means more fuel used.

“We see this across the United States as well,” DePodwin added. “I think it was a Boston-to-Phoenix flight many years ago that actually had to stop to refuel somewhere in the middle of the county, like Oklahoma, because of a significant head wind."

At a time when numerous airlines have bemoaned high costs, including fuel prices, as a proverbial head wind, they’ll likely take any literal tail wind they can get.

“There’s definitely a lot of aviation logistics that come into play,” DePodwin said. “Weather is a big factor.”

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