Helicopters fly over Tian'anmen Square in the formation of "100" ahead of a grand gathering celebrating the Communist Party of China (CPC) centenary at Tian'anmen Square in Beijing, capital of China, July 1, 2021. (Photos by Yin Gang/Xinhua)

Military aircraft fly over Tian'anmen Square in echelon ahead of a grand gathering celebrating the Communist Party of China (CPC) centenary in Beijing, capital of China, July 1, 2021.

Military aircraft fly over Tian'anmen Square in echelons ahead of a grand gathering celebrating the Communist Party of China (CPC) centenary in Beijing, capital of China, July 1, 2021.

Military aircraft fly in echelons ahead of a grand gathering celebrating the Communist Party of China (CPC) centenary in Beijing, capital of China, July 1, 2021.

Military aircraft fly in echelons ahead of a grand gathering celebrating the Communist Party of China (CPC) centenary in Beijing, capital of China, July 1, 2021.

Military aircraft fly over Tian'anmen Square in echelons ahead of a grand gathering celebrating the Communist Party of China (CPC) centenary in Beijing, capital of China, July 1, 2021.

Military aircraft fly in echelons ahead of a grand gathering celebrating the Communist Party of China (CPC) centenary in Beijing, capital of China, July 1, 2021.