A Jet Airways flight between Mumbai and Jaipur in India, had to return to Mumbai on Sept 20 due to cabin pressure dropping that led to bleeding from nose and ear of passengers on the flight.

Jet Airways a major Indian international airline based in Mumbai said that it “regretted” the incident.

An official of India’s Directorate General of Civil Aviation (DGCA) said that the aircraft had air turnback to Mumbai, as cabin pressure fell due to the fault of cockpit crew. Jet Airways has derostered pilots pending investigation.

“During climb, crew forgot to select bleed switch due to which cabin pressurisation could not be maintained. As a result, oxygen masks got deployed,” said an official. He added: “Thirty out of 166 passengers experienced nose and ear bleeding, some also complained of headache.”

“The flight’s cockpit crew has been taken off scheduled duties pending investigation,” the airline said in a statement. The airline made alternative flight arrangements for passengers on this flight.

“All guests were deplaned safely and taken to the terminal. First aid was administered to few guests who complained of ear pain,” the statement added.

Aircrafts usually travel between the altitudes of 28,000 and 35,000 feet, where air pressures are significantly lower than those on the earth’s surface. To counter this, aircraft cabins must  be pressurized to maintain safe levels of oxygen. Without pressurization, the air becomes drier and thinner, leading to compromised membranes in the ears and nose, which may cause pain and bleeding.

An official at India’s Aircraft Accident Investigation Bureau (AAIB) said going by the preliminary information, it could be a case of negligence on the part of the pilots since controlling cabin pressure control is part of check before operating a flight. Serious incidents and accidents are referred to the AAIB for further investigation.