Transatlantic airplanes are flying at the 'speed of sound' right now. Here's why

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Savior of many a cramped pair of legs, the jet stream is well known for lopping roughly an hour off long haul west-to-east flights.

But it's working especially hard for travelers in economy class right now, with the jet stream over the Atlantic so strong that flights heading from the US to Europe are reaching speeds equivalent to that of sound.

Sound travels at about 761 mph or 1,100 feet per second in "sea level standard conditions," according to NASA - a little over 661 knots.

In the past 24 hours, passenger aircraft traveling east from the US across the Atlantic have reached up to 778 mph. That's a little over 200 miles per hour faster than normal cruising speeds.

But if you're thinking these flight times are a match for the much-missed Concorde, whose sonic booms used to mark it breaking the sound barrier, it's time to think again. There's a difference between ground speed and speed in the air (indicated air speed, essentially the speed of the plane in relation to the air around it). These passenger flights, however speedy, didn't break the sound barrier.

But they did slash flight times. Emirates flight 222 from Dallas to Dubai arrived 57 minutes early on November 1, having reached a top speed of 675 knots, or 777 mph, off the coast of Newfoundland, according to flight tracking site Flightaware.