Jet streams have been making headlines this week, with a commercial flight by British Airways said to ‘approach supersonic speed’, due to the advantage of a massive tail wind.
The Boeing 777 was propelled at ground speeds of up to 745mph on a flight from New York to London Heathrow, with a flight time of 5 hours and 16 minutes. This is a flight that takes 6 hours or more on average, though airlines schedule the route at around 7 hours, to allow for variances.
In fact wind direction and speed can make a flight time quite different, for exactly the same journey. And it’s not uncommon at this time of year for pilots to save a lots of time against schedule on a eastward-bound Atlantic flight. Other flights in recent days – including our private jet flights – have also seen significant chunks shaved off their flight times, thanks to the current jet stream’s winter surge.
What is a jet stream?
Jet streams are strong westerly winds that blow in a narrow band in the Earth’s upper atmosphere – at the altitudes used by most aircraft. Where these packets of fast moving air form a tube, they are called jet streams.
By flying in a jet stream, aircraft travelling from west to east get carried along by the tailwind, saving them time – and/or fuel. In fact most airline pilots are trained to reduce airspeed when the winds are so much to their advantage, to save fuel costs – not to fly in the shortest possible time. Private jet pilots nearly always fly as fast as possible but would of course speak to the customers on-board to ensure that an early arrival time is acceptable.
The North Atlantic jet stream typically reaches its peak intensity during January and February, when the temperature contrast between the equator and the North Pole is largest.
The intensity of the jet stream also has a big impact on the weather. Which is why the US is currently seeing a return of the polar vortex-related cold.
Airspeed and ground speed are not the same thing though. The actual airspeed of the 777 aircraft was considerably lower than 745mph. The aircraft was flying within normal design limits, well below the speed of sound at altitude.
What is ground speed?
Aircraft fly relative to the air around them. In the case of a tail wind the air around an aircraft is also moving, so the combination of the speed of the aircraft and air it is flying in results in a greater ground speed.
Of course a head wind will also reduce the ground speed of an aircraft. Flying in the other direction across the Atlantic – ie Europe to US – can take significantly longer when the jet stream is at its peak and headwinds are bellowing from west to east across the ocean. Flights sometimes take an unusual route to avoid this – such as flying closer to Greenland, rather than heading due west across the Atlantic.
How are take off and landing affected by winds?
Aircraft always take-off and land into the wind to reduce the ground speed.
Cross winds can also make take off and landing challenging for pilots. So airports will impose limits if the wind is moving across the runway. Many airports have runways facing in different directions to mitigate against cross winds, allowing the pilots to use the runway that faces into the wind.
When it comes to speeding up your travel time, private jets make shorter work of any journey – regardless of the wind direction. Not only in actual flying time – although speed rivals the Gulfstream G650 and Citation X are faster than commercial airliners – but on the ground. When you can arrive just minutes before take-off and use smaller airports closer to your destination, your journey will be faster, whatever the weather.
For advice on the timing for your private jet itinerary timing contact us or call our 24/7 Flight Team on +44 1747 642 777.