A Boeing 787-9 twin jet on a Virgin Atlantic flight from Los Angeles to London peaked at a whopping 801 mph some 35,000 feet over Pennsylvania.

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Airplanes flying through the jet stream, the high-altitude air current along which storms travel, will either be sped up or slowed down big time, depending on their direction of travel. It’s like the moving walkway at the airport. You have your own forward speed, but if you continue this velocity in an environment that is itself moving, it can propel you at an impressive rate.

On Monday the jet stream was clocked at more than 230 mph over Long Island and a Virgin Atlantic flight from Los Angeles to London peaked at a whopping 801 mph, 35,000 feet over Pennsylvania. “[N]ever ever seen this kind of tailwind in my life as a commercial pilot,” tweeted Peter James, a jet captain.

It appears that’s a record for the Boeing 787-9 twin jet, which in the past has flown at speeds up to 776 mph. The ordinary cruising speed of a Dreamliner is 561 mph, with a maximum propulsion of 587 mph. Any speed gained on top of that is thanks to Mother Nature’s helpful boost.

Although the plane didn’t remain in the “jet streak” — the zone of maximum wind embedded within the jet stream — for long, it still arrived 48 minutes early. And you might notice something suspect about the 801 mph reading — it’s above the speed of sound (767 mph). Commercial aircraft ordinarily can’t break the sound barrier, because they’re not designed to handle the sudden increase in drag and other aerodynamic effects associated with those speeds. Despite a ground speed that high, the plane didn’t come close to reaching that threshold because it was embedded in the swiftly moving air.

An LAX-JFK Delta flight overnight hit 678 mph at 39,000 feet over the Ohio Valley, while a 737 from Chicago to New York passed 700 mph Tuesday morning. Chicago to New York/Boston routes will be shortened to 1 hour, 24 minutes Wednesday instead of the usual nearly two-hour flight time. Likewise, flight times from Dallas to Boston dipped below three hours, with an Embraer ERJ-190 twin jet achieving 739 mph in the jet streak.

Storms cause the jet stream to bend, cresting and dipping into waves that ride across the Lower 48. Just like kinking a garden hose, it causes the flow speed to decline. In the absence of large-scale weather systems, a zonal west-to-east jet is free to gather considerable speed, much like how we reach our fastest highway speeds on straightaways.

The jet stream can usually get to speeds this high only in the winter because temperature differences between the north and south are maximized. Temperatures on Tuesday hovered around minus-10 to minus-20 in eastern Canada while soaring well into the 80s over Florida. Such large differences in temperature (and pressure) power the wind.