'September 13 Incident') was an aircraft accident at 3 a.m. on 13 September 1971 involving Lin Biao, the Vice Chairman of the Chinese Communist Party.

Everyone on board the Hawker Siddeley Trident, including Lin and several members of his family, died when the aircraft impacted Mongolian terrain.

[2] According to the Chinese government, Lin Biao was made aware that Mao no longer trusted him after the 9th Central Committee, and he harbored a strong desire to seize supreme power.

[3] Mao was unaware of the coup plot, and, in August 1971, scheduled a conference for September to determine the political fate of Lin Biao.

After hearing that Premier Zhou Enlai was investigating the incident, they abandoned this plan as impractical, and decided to flee to the Soviet Union instead.

Many of the original government records relevant to Lin's death were secretly and intentionally destroyed, with the approval of the Politburo, during the brief period of Hua Guofeng's interregnum in the late 1970s.

Skeptics assert the official narrative does not sufficiently explain why Lin, one of Mao's closest supporters and one of the most successful Communist generals, would suddenly attempt a poorly planned, abortive coup.

Skeptics have claimed Lin's decision to flee to the Soviet Union was illogical, on the grounds the United States or Taiwan would have been safer destinations.

[4] One theory attempted to explain Lin's flight and death by observing that he opposed China's rapprochement with the United States, which Zhou Enlai was organizing with Mao's approval.

[10] A six-month investigation by Western scholars in 1994 examined evidence in Russia, Mongolia, mainland China, the United States, and Taiwan, and came to a number of conclusions, some of which were contrary to the official Chinese version of events.

Several senior leaders within the Communist Party hierarchy knew Lin and his family would flee, but chose not to attempt to stop their flight.

The eyewitness account of Zhang Ning, who was Lin Liguo's fiancée before his death, and another witness who requested anonymity, indicate a sequence of events different from the official narrative.

[11] At 10 p.m. the night before Lin's party fled, Ye Qun announced the family would board an aircraft at 7 the next morning to fly to Guangzhou.

At 11:30, Ye Qun called Zhou and informed him Lin Biao was planning to fly to Dalian, and denied they had prepared an aircraft at Shanhaiguan.

According to the driver of Lin's limousine, there was no time to place mobile stairs next to the aircraft's entrance, so the party boarded via a rope ladder.

The team removed the heads of two of the corpses suspected to be Lin Biao and Ye Qun and took them back to the Soviet Union for forensic examination.

In order to corroborate their findings the team returned to Mongolia a second time to inspect the body believed to be Lin Biao's.

After exhuming the body a second time the team found remains of tuberculosis — which Lin had suffered from — in the corpse's right lung, confirming the Soviet identification.

The Soviet team was not able to determine the cause of the crash, but hypothesized the pilot misjudged his altitude while intentionally flying low to evade radar.

All of the work and its results were kept secret from the public: outside of the investigative team, only KGB chairman Yuri Andropov and Soviet leader Leonid Brezhnev were informed.

[4] On 14 September, Zhou announced to the Politburo that four of the highest-ranking military officials in China were immediately suspended from duty and ordered to submit self-criticisms admitting their associations with Lin.

Without the support of Lin, Jiang was unable to prevent Zhou's efforts to improve China's relationship with the United States, or to rehabilitate cadres who had been purged during the Cultural Revolution.

[24] Throughout the 1970s, high-ranking leaders of the Chinese Communist Party, including Hua Guofeng, spread the story to foreign delegates that Lin had conspired with the KGB to assassinate Mao.

Much of this propaganda campaign involved the creative falsification of history, including (false) details about how Lin had opposed Mao's leadership and tactics throughout his career.

In 1981, the government released their verdict: that Lin Biao must be held, along with Jiang Qing, as one of the two major "counter-revolutionary cliques" responsible for the excesses of the late 1960s.

[4] According to the official Party verdict, Lin and Jiang were singled out for blame because they led intra-Party cliques which took advantage of Mao's "mistakes" to advance their own political goals, engaging in "criminal activity" for their own self-benefit.

In 2007, a big portrait of Lin was added to the Chinese Military Museum in Beijing, included in a display of the "Ten Marshals", a group considered to be the founders of China's armed forces.