Wu Xiaobo, a Chinese doctor, assists with two in-flight medical emergencies while travelling recently to and from the US. [Photo/Screenshot from CCTV]

A Chinese doctor on board a United Airlines flight is being hailed as a hero after saving the life of a passenger who possibly suffered a stroke mid-flight, reports the Beijing Youth Daily.

Wu Xiaobo, a thoracic surgery doctor with the People's Hospital of Wuxi, was flying to Los Angeles on Sept 29, 2017, when a fellow passenger fell unconscious and began vomiting.

Responding to an in-flight announcement for a doctor, Wu heeded the call, determining the man in his 50s likely suffered a stroke.

"Cerebral infarction patients may suffer another stroke, and possibly die, if they don't receive timely treatment," said Wu.

Wu Xiaobo (Right) helps assist a female passenger who passes out on his China Eastern flight on Oct 10, 2017. [Photo/Screenshot from CCTV]

He recommended an emergency landing, and two hours later, helped escort the stricken passenger off the flight in San Francisco.

And this wasn't the last time the doctor was called upon to help out a fellow air traveler.

Heading back to China on the same trip, Wu Xiaobo helped assist a female passenger who passed out on his China Eastern flight on Oct 10.

The young lady fainted, but managed to regain consciousness with the help of the doctor.

Asked about the incidents, a humble Wu Xiaobo is being quoted by the Beijing Youth Daily as saying simply that it's "what a doctor is supposed to do."