Bumpy ride? The invisible cause of a turbulent flight.

JOLT! Who of us hasn’t found ourselves rudely stirred from our slumber at 10,000 metres, mid-flight, with the contents of our coffee cups heading from our drinks tray into our nearest neighbour’s lap. Our nice straight aisle is transformed into a zig-zag assault course, which only the boldest of cabin crew can take on. A superhuman external force has grasped our plane and is shaking it playfully, just as a child would do to its toy. As the supersonic rattle goes on and on, even the most hardy of travellers begins to wonder how much longer the puny nuts and bolts can withstand the onslaught and keep this hollow lump of metal together.

Modern aeroplanes can withstand all but the most severe turbulence.

Then suddenly the mayhem stops. Out of nowhere, tranquility resumes and 200 passengers breathe a collective sigh of relief. We WILL survive. Oddly, all the while, the weather out of our window has remained apparently serene. Clear skies. No thunderclouds. No lightning. Not so much as a cloud between us, the deep blue seas below and outer space above.

Clear Air Turbulence (CAT) is usually the cause. Small, rapidly spinning swirls of air – invisible, perhaps just a few metres across, yet awesomely powerful. Planes have been known to lurch hundreds of metres in seconds due to the imbalance in air pressure that these atmospheric whirlwinds cause. Yet despite the din, the juddering and the odd flying suitcase, more serious consequences are rare. Modern aeroplanes can withstand all but the most severe turbulence.

Meteorological computers have got quite good at predicting where CAT is likely to occur as well. This information is relayed to pilots in order that they can avoid such turbulence. But just occasionally, nature confounds the experts and out of nowhere, the 0817 from London to New York goes all of a judder. How then to calm the nerves?

Time for another Bloody Mary?