Lin Biao Incident
Also called: September 13 Incident, Project 571, Criticize Lin, Criticize Confucius
On 13 September 1971 Lin Biao, Mao Zedong’s designated successor, fled China by air with his family; the plane crashed near Öndörkhaan in Mongolia, killing all on board. The Chinese government announced that he had fled after a coup plot was exposed, but much about the affair remains unclear.

unknown Mongolian photographer · Public domain · Source
At the Ninth Party Congress in 1969 Lin Biao was written into the party constitution as Mao’s “close comrade-in-arms and successor”. But at the 1970 Lushan plenum he fell out with Mao over a proposal to revive the post of head of state, and Mao then criticised and curbed the generals around him. According to the Chinese government, Lin’s son Lin Liguo drafted a coup plan, the “Outline of Project 571”, and plotted to assassinate Mao.
On the night of 12 September 1971 Lin, staying at Beidaihe, boarded a Trident airliner at Shanhaiguan airport with his wife Ye Qun and Lin Liguo; it took off in the early hours of the 13th, flew north and crashed on the steppe north-east of Öndörkhaan in Mongolia, killing all nine aboard. The Chinese government said it had run out of fuel while attempting a forced landing. The affair was at first disclosed only within the party and was made public in 1972.
The flight and death of the designated successor badly damaged the legitimacy of the Cultural Revolution and left many disillusioned with it. Deng Xiaoping was rehabilitated in 1973, the year the “Criticise Lin, Criticise Confucius” campaign began.