15 passengers injured in 'serious' mid-air incident on Qantas flight.

Australia’s air safety watchdog is investigating a serious mid-air incident involving a Qantas jet that suffered a so-called “stick shaker” warning, injuring 15 passengers.

The drama unfolded about 110km southeast of Hong Kong last Friday after flight QF29 took off from Melbourne.

The “stick-shaker” device causes the aircraft’s control stick to vibrate noisily to warn the pilot of an imminent stall. It takes a physical, rather than visual, form so the crew will be alerted even if they are not looking at the panel.

The Australian Transport Safety Bureau classified the Boeing 747’s incident as serious and said a report would be released “within several months” after it interviewed the flight crew.

“The flight crew disconnected the autopilot and manoeuvred the aircraft in response,” it said.

“Fifteen passengers received minor injuries.”

The incident is understood to have lasted about two minutes and while the flight landed normally in Hong Kong, an ambulance met passengers as a precaution and one person was taken to hospital for assessment.

Qantas said customers experienced “unexpected in-flight turbulence” during the trip.

“We notified the ATSB of the occurrence, and our own teams are also reviewing the event,” a spokeswoman said.