UNRELATED to the crash of China Southern Airlines MU5735. FACT: the shared video appeared previously in 2016, related to the mountain fire in Yishan Village, Zushan Town, Qinglong County, Qinhuangdao, Hebei Province, China.
More in the EXPLANATION and REFERENCES section.
CATEGORY: False Context.
SOURCE: Twitter, https://archive.ph/EOsv8 (backup archive).
NARRATIVE: “RIP Mu5735 plane crash – 133 people on board #planecrash #mu5735 #boeing #boeing737 #Chinese”.
Based on 7 Types of Mis- and Disinformation by First Draft News, classified as “False context: When genuine context is shared with false contextual information.” 
The SOURCE shared a 2016 mountain fire video which occurred in Yishan Village, Zushan Town, Qinglong County, Qinhuangdao, Hebei Province, China with false contextual information, which has caused FALSE conclusion.
Video with correct context, uploaded to Youku on April 1st 2016: “Qinglong Zushan fire, residents evacuated” 
Other Related References
Tianjin Daily on March 31 2016: “#zushan fire# [A mountain fire broke out in Zushan, Qinhuangdao City, Hebei] At two o’clock this afternoon, a mountain fire broke out in Zushan, Qinhuangdao City, Hebei. Due to the strong wind, the fire was getting bigger and bigger, and the smoke spread more than ten kilometers away. The steep mountain made it very difficult to fight. Because there is a gas station at the foot of the mountain, for safety, firefighters and nearby villagers are temporarily evacuated. There are no specific casualties and fire area figures. (Voice of China)” 
Sina News on March 31 2016: “This afternoon, a mountain fire broke out in Yishan Village, Zushan Town, Qinglong County, Qinhuangdao, Hebei Province. The flames surrounded the gas station at the foot of the mountain, and the surrounding people were evacuated urgently. As of 5:30 p.m., the mountain fire leading to the Zushan Scenic Spot has been extinguished, and the remaining fires have been initially controlled with no casualties. The cause of the fire is under investigation. Beijing reporter Nie Hui http://t.cn/RqAZpzm” 
Related to the crash of China Southern Airlines MU5735, Google Search – News 
 news.sina.com: “A mountain fire broke out in Zushan Town, Qinhuangdao? The scene is on fire”, https://archive.ph/SICFI (Google Translate Chrome extension) / https://bit.ly/3iPJ9yY & https://archive.ph/g0yZ1 (link and backup archive in original language, Chinese).
 google.com: “china southern airlines MU5735 crash”, https://archive.ph/GzFnt (backup archive).