India's West Bengal Chief minister Mamata Banerjee suffered a back injury after her flight, on which she was returning to Kolkata from Varanasi on Friday evening, encountered a spot of air turbulence, causing the plane to shake erratically.

The pilot, however, managed to steer the chartered flight away from the air pocket and land safely.

"The chief minister is already recuperating from a back pain. This incident flared it up again," said Trinamool spokesperson Kunal Ghosh, adding, "There was a lot of anxiety and panic on the flight due to the sharp altitude drop."

A senior airport official said the pilot had reported to the air traffic control about turbulence at a certain level, seeking permission to descend at a different level, in order to avoid it. "The ATC gave permission, and so the pilot descended from that level and landed the flight safely. We haven't received any complaint from the chief minister or the state government regarding the incident," he added.

Weather officials said there was no turbulence forecast and the weather condition that had developed was sudden and extremely localised.

Clear-air turbulence, causing erratic air currents, usually occur in cloudless air between altitudes of 20,000ft and 49,000ft and are considered a flight hazard. "This turbulence can be caused by small-scale wind velocity gradients around the jet stream, where rapidly moving air is close to much slower air," a weatherman said.

However, the CM's aircraft was at an altitude of 7,000ft, about 50km northwest of Kolkata, when it encountered the phenomenon. "There was no turbulence forecast but such localised turbulences occur from time to time. Had it been a larger craft, the passengers would have faced less, or no turbulence on most occasions," an official said.

Source: The Times of India