Long Qiming, 91, the only remaining Flying Tiger pilot on the mainland, is seriously ill and on a respirator at a hospital in Chongqing. XINHUA

A 91-year-old former Flying Tigers pilot, the only one still alive on the Chinese mainland, is critically ill with a lung infection.

Long Qiming, who joined the Flying Tigers in 1943, is now in a Chongqing hospital.

"The hospital has told me that he is gravely ill," said Long's wife Peng Tianming, 72.

The doctor, Pu Xia, who is in charge of Long's treatment at the No 1 Hospital affiliated with Chongqing University of Medical Science, said Long's pulmonary infection is serious, adding that he could suffer respiratory failure, septic shock or multiple organ failure at any time.

"We are trying our best to save him," the doctor said.

As the youngest pilot of the Flying Tigers, Long's life has been as legendary as the fighter group, which was composed of volunteer US pilots and pilots recruited from China who were trained by a retired US Army Air Corps officer to help China resist Japan in World War II.

Born in 1923 to a wealthy family in Hong Kong, Long received a good education and speaks fluent English. He and his brother fled to the Chinese mainland in 1942 when Hong Kong was invaded by the Japanese. His parents were killed by Japanese troops when they came to find them.

He gave up the opportunity to become a pilot in the US after the war, saying "my roots are in China" and that he wanted to help rebuild his homeland.

He remained one of China's first generation of pilots until 1953 when he was transferred to the Chongqing Steel and Iron Plant, where he retired as an engineer in 1983.

He donated his family's ancestral residence－a grand house dating to the Qing Dynasty (1644-1911) in Shunde, Guangdong province, to the local government in 2011. The house has now become a historic venue.