A passenger plane had to turn back mid-flight after pilots apparently forgot to maintain cabin pressure.
Passengers on the Jet Airways flight from Mumbai to Jaipur in India complained of bleeding from their noses and ears not long after takeoff.
Videos and photos posted online showed oxygen masks being deployed.
India's Ministry of Civil Aviation said 30 of the 166 people on board had received medical treatment.
Transport official Lalit Gupta told the Hindustan Times that the crew forgot to press a switch that would have maintained cabin pressure.
"As a result, oxygen masks got deployed," he said.
Jet Airways said the flight's cockpit crew had been taken off scheduled duties "pending investigation."
In a statement, the Indian airline said the flight "made an air turn back due to loss in cabin pressure. The B337 aircraft, with 166 guests and 5 crew landed normally in Mumbai. All guests were deplaned safely and taken to the terminal. First aid was administered to few guests who complained of ear pain, bleeding nose etc."
The statement added that the company was "making alternative flight arrangements for guests on this flight. Jet Airways regrets the inconvenience caused to its guests."