Chinese authorities and Airbus are investigating why a plane’s cockpit windscreen detached during a flight, forcing an emergency landing.

Sichuan Airlines flight 8633 was en route from Chongqing, China, to Lhasa, Tibet, on Monday morning when the cockpit window on the A319 jet flew off, the country’s aviation regulator said.

The co-pilot’s seatbelt prevented him from being sucked out of the plane.

The plane took off at 6.27am and had risen to 9,800 metres when its right-hand windscreen “suddenly burst and fell off, causing the cabin to lose pressure and passenger oxygen masks to drop”, the Civil Aviation Administration of China said.

Air crew with the Sichuan Airline flight in Chengdu
Air crew with the Sichuan Airlines flight in Chengdu (Passenger/AP)

“There was no sign before the windshield burst. Just a huge noise,” Captain Liu Chuanjian said, according to Chinese state media reports.

When he looked across the cockpit, he saw “the co-pilot was partially blown out of the aircraft. Luckily, he had the belt buckled up”.

Some cockpit equipment was damaged, the CAAC said. Photos posted on Chinese social media showed a control panel partially torn away from the dashboard.

The jetliner made an emergency landing in Chengdu, China.

The co-pilot suffered scratches, a flight attendant’s waist was hurt, and 27 of the 119 passengers were injured, according to a post from Sichuan Airlines on Sina Weibo, China’s version of Twitter.

Airbus said it has assigned a team to investigate and will co-operate with Chinese authorities.

CAAC said the Airbus jet began service on July 26 2011 and had no record of defects. It had not undergone any major maintenance before the accident.

It is exceedingly rare, though not unprecedented, for a jet’s windscreen to blow out.

In 1990, an improperly installed screen on a British Airways jetliner detached after it took off from Birmingham Airport. The captain was sucked halfway out of the opening but the crew managed to make an emergency landing.

Earlier this year, a Southwest Airlines jet’s passenger window shattered when it was hit by debris from an exploding engine, killing one passenger.