A Sichuan Airlines flight has been forced to make an emergency landing in the southwest Chinese city of Chengdu on Monday after a windshield on the right side of the jet’s cockpit broke off, China’s aviation authority said.

No passengers were injured in the incident but the pilot sitting in the right seat, who is usually the first officer, suffered scratches and a sprain, the Civil Aviation Administration of China’s (CAAC) Southwest Regional Administration said on its website.

A cabin crew member was also injured in the descent, it added, without providing details on what had caused the windshield to break off.

The flight, Sichuan Airlines 3U8633, left the central Chinese municipality of Chongqing on Monday morning and was bound for the Tibetan capital of Lhasa, the authority said.

According to flight tracking website FlightRadar24, the aircraft was an Airbus A319. A spokeswoman for Airbus said that the planemaker would provide all necessary support upon request by the CAAC and Sichuan Airlines.

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Sichuan Airlines said on its official Weibo account that the flight had experienced a “mechanical failure” without providing further details. It said it had switched the flight’s passengers to another aircraft to carry on their journey to Lhasa.

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Pictures published by government-run Chengdu Economic Daily showed the plane missing one of its cockpit windows and damage to its cockpit controls. Chinese social media users praised the pilots for landing the flight safely without incurring any passenger injuries.

Sichuan Airlines, a regional airline headquartered in Chengdu, operates mostly domestic flights but also flies internationally to countries such as Japan, Canada and the Czech Republic.

Incidents involving cracked windshields do happen on a regular basis due to occurrences such as bird or lightning strikes but ones involving entire windshields coming off are rare.

In 1990, one of the pilots on British Airways Flight 5390 was blown partially out of the cabin window after its windshield blew out at 23,000 feet. He survived the incident, which occurred on a BAC-111 jet.

#BREAKING Sichuan Airlines flight makes emergency landing in Chengdu from Chongqing on its way to Lhasa; reason remains unclear pic.twitter.com/q4haElhaFe — CGTN (@CGTNOfficial) May 14, 2018

An engine on a Southwest 737 in April ripped apart in flight and shattered a cabin window, killing a female passenger in the first U.S. airline passenger fatality since 2009.

On May 3, another Southwest Airlines flight made an emergency landing after a cabin window pane cracked in flight.