With eight passengers of a Kolkata- bound Vistara flight suffering injuries yesterday when the aircraft was caught in air turbulence near Kolkata airport, aviation experts felt one ought to investigate whether the passengers concerned had their seat belts on.

With the meteorological department predicting early monsoon, Bengal has been witnessing thunderstorms and gusty wind accompanied by intermittent but heavy showers. The Meteorological Terminal Air Report (METAR) for Kolkata airport today forecast the possibility of the formation of cumulonimbus clouds.

On 7 June, the Vistara flight UK775, a Boeing 737-8AL aircraft, was on its way from Mumbai to Netaji Subhas Chandra Bose International (NSCBI) Airport, Kolkata. However, the aircraft fell into a turbulent air pocket about 25 nautical miles from the airport. This left eight passengers injured. Two persons with serious injuries like fractures are admitted to a city hospital. The flight landed safely at 4:25 pm. The DGCA has begun a probe into the incident.

A senior pilot and flight instructor of an eminent Indian airline, requesting anonymity, told The Statesman, “I hope in the investigation, priority will be given in checking whether the seatbelt sign was on and find out if passengers concerned were following the protocol. It is often passengers don’t put on their seat belts or just pretend to have. The flight crew needs to inspect in-flight. This must be taken into account by investigators before considering secondary angles like a pilot error.”

The pilot explained, “We come across both clear air turbulence (CAT) and weather turbulence. We get pre-flight weather reports and decide accordingly. But, at times even weather radars could malfunction or it can be a sudden weather change. It then depends on the pilot’s expertise to manouvre out of it. But passengers must wear their seat belts properly when the pilot puts on the sign to do so.”

Asked whether there are any specific rules as to when seatbelts are compulsory, the pilot said, “As per rules followed by airlines, all aircraft below 10,000ft need to compulsorily put on the sign for wearing seat belts. However, beyond that altitude, it depends on the rules of the airlines.” In this case, as per sources, the Vistara flight was between 20000 ft to 17000ft altitude when it happened.

It was pointed out, that after such incidents, checks are made to ascertain whether the aircraft sustained damages. The Boeing aircraft concerned was grounded at Kolkata airport to carry out inspections, airport sources said. “In such incidents, the damage is often noticed on the wings,” said the senior pilot concerned.