Boeing 737-800 jetliner has once again been put in operation in China, less than a month after the aircraft crashed in the mountains of Guangxi. The incident killed all 132 people on board, some of them being crew members.

According to data from Flightradar24, a plane tracking website, the China Eastern flight MU5843 flight took off from Kunming around 10 AM on Sunday and landed in the southwestern city of Chengdu an hour later.

Also Read: What’s next in China Eastern plane crash investigation?

According to the website, the Boeing 737-800 aircraft conducted a test flight on Sunday morning in COVID-19 rattled Shanghai, where the airline is based. Another test flight was conducted a day before in Chengdu, from where the plane departed to Kunming.

The investigation of the crash, which happened on March 21, is still underway. The two black boxes recovered from the aircraft were sent to the United States earlier this month for further investigation.

The National Transportation Safety Board said it is helping its Chinese counterparts download information from the flight data recorder. The American agency said last week it was doing the same for the cockpit voice recorder.

Also Read: China plane crash: Terror attack, suicide not ruled out as cause, report says

Both may have been damaged by the impact of the crash. If the information on them can be recovered, it could shed light on why the China Eastern Boeing 737-800 went into a sudden nosedive and slammed into the ground in a mountainous area on March 21.

The crash left a 20-meter- (65-foot) deep crater in a mountainside, shattered the plane and set off a fire in the surrounding forest. More than 49,000 pieces of plane debris were found. It took two days to find the cockpit voice recorder and six days for the flight data recorder, which was buried 1.5 meters (5 feet) underground.