Two wheels were found missing on an airplane that made an emergency landing in Shenzhen, south China's China's Guangdong Province on Tuesday. Five people were slightly injured among the nine crew and 166 passengers on board. The rest of the passengers and crew were evacuated safely, according to airport authorities. It was the second incident in a week for Chinese budget carrier Capital Airlines.

Flight JD5759 bound for Macao made an emergency landing on August 28 after a mechanical failure. The failure was likely due to bad weather, according to a report released by the carrier on China's Twitter-like Weibo.

Wheels are missing. /Photo via the Paper.

"Capital Airlines flight JD5759 took off from Beijing International Airport at 8:17 am, and was suspected of encountering wind shear while landing at Macao," Capital Airlines said on Weibo.

"The crew concluded that landing gear may have been damaged," it said, adding that the crew aborted the landing to make an emergency landing in Shenzhen.

Capital Airline's announcement. /Screenshot on Weibo.

In response, the Civil Aviation Administration of China (CAAC) announced it would launch an investigation into the incident. The two wheels were reported missing and the landing gear was damaged.

The five injured passengers on JD5759 were discharged from the hospital by Wednesday night. While the others evacuated were rescheduled on different flights or refunded, said Capital Airlines.

The simulation landing. /Gif via the Paper.

Wind shear is an atmospheric phenomenon which happens when the wind speed or direction varies over a short distance. Strong wind shear is also recognized as the "invisible killer" for the aircraft, especially when the aircraft is climbing or descending under 600 meters height, as it can cause catastrophic results.

"The wind shear may result in sudden loss of air pressure or cast difficulty in steering the direction for the pilot," said Chen Jianguo, the leader of Aircraft Owners and Pilots Association Of China (AOPA) in an interview with the Paper, "It could be an original cause of the incident. But further investigation is necessary before drawing the conclusion."

Flight JD5759 landed in Shenzhen. /VCG Photo.

It was the second incident to happen in one week for Capital Airlines. On August 26, another flight JD5158 returned to its departure city due to a mechanical failure. The flight suffered a 20-minute-long mid-air plunge and a 4,000 meter height emergency descent during the trip, triggering the deploy of oxygen masks. Fortunately, the nine crew members and 146 passengers all landed safely.