Four passengers aboard an Air India Express aircraft from Muscat in Oman to Kozhikode in Kerala suffered nosebleeds, and some other had an earache allegedly because of problems with the aeroplane’s cabin pressure soon after takeoff on Sunday. The aircraft, carrying 185 passes, returned to Muscat airport following the incident, The Times of India reported.

Air India Express Flight IX 350 took off from Muscat airport around 3.19 am local time (4.49 am India Standard Time) on Sunday. The flight climbed up to a height of 12,000 feet before the passengers started experiencing discomfort. Following nosebleeds and earache, the plane was taken back to the airport.

There, airport doctors treated the four passengers and pronounced them fit to fly. The passengers who suffered earache recovered after the aircraft landed, Air India Express Chief Executive Officer K Shyam Sundar told the newspaper. The airline has reported the incident to the Directorate General of Civil Aviation, which has initiated an investigation.

“Replacement crew and spares reached Muscat on Sunday morning,” Sundar said. “The aircraft, after due rectification and verification left the airport at 2.15 pm local time [3.45 pm IST].”

“The crew which operated IX 350 would have had exceeded its maximum duty time, so a replacement crew had to be arranged to fly the plane to Calicut,” another airline official said.