Last Thursday, passengers flying from the US to Europe were in for a treat: their trips were nearly an hour shorter than usual.

Did pilots push the trust levers up to get them there in record time? Nope. They rode a wave of 200 mile-per-hour jet stream blowing across the Atlantic. One flight in particular, British Airways Flight 114, completed its trip from JFK to London Heathrow in just 5 hours and 16 minutes. The route normally takes over 6 hours to complete. It's no wonder that British Airways' callsign is "Speedbird."

Jet stream velocity during BA114 flight / earth.nullschool.net

Approaching Supersonic Groundspeed

On Flight 114, the Boeing 777 reached ground speeds of 745 MPH. To put that speed in perspective, the speed of sound at sea level is just over 761 MPH, and at the 777's filed altitude of 35,000 feet, the speed of sound is about 661 MPH.

So does this mean the aircraft broke the speed of sound? Nope. In fact, it was probably flying at the exact same indicated airspeed it always does on the route. It was just being pushed by the wave of extremely fast jet stream air. So even though its ground speed was fast, the jet's indicated airspeed was the same as always.

Route of flight from JFK to LHR / FlightAware.com

High Speeds In The North Atlantic

Peak speeds of the North Atlantic jet stream, called the polar jet, usually happen in the winter. Why winter? Jet streams are created by a combination many things, like the Earth's rotation on its axis, but one of the most significant influences on jet stream speed is a large temperature difference between air masses. And because it's currently winter in the Northern Hemisphere, the largest temperature difference between the equator and north pole is happening right now.

Clouds along jet stream over Canada / Wikipedia

The polar jet is typically exists between 23,000 to 39,00 feet MSL, which is another reason airliners are able to ride the wave (in contrast, subtropical jet streams are higher - usually 33,000 to 52,000 feet MSL). This means that almost every flight between the US and Europe is flying in the altitude band of the jet stream.

It's Not All Good News

Even though airliners are riding the jet stream and getting to Europe in record time, it's not always good news. Clear air turbulence (CAT) is often found in the regional boundaries of jet streams, and it can make for a pretty uncomfortable ride.

The Flight Home

If you're looking forward to a speedy trip to London, it looks like the flight times are still pretty good. Over the last 8 days, every trip has been under 6 hours. But enjoy the ride there, because your trip home is going to be much longer; you'll be fighting a 120+ knot headwind.