En route from Adelaide to Bali, a Jetstar flight an hour and a half in was turned around after passengers heard strange noises.

Flight JQ127 departed Adelaide Airport just after 7pm on Friday but turned back near Marla in the state's Far North about an hour into the flight.

It landed safely in Adelaide about 9.30pm.

Chantelle Giannopous told 7 News, "It was an intense moment and bit scary. There were people crying. I guess just the unknown.

"When we landed it was shaking a fair bit, like pretty scary stuff and it was going a lot faster than normal when you land.

"There were the fire brigade and stuff waiting for us. It was pretty scary."

The flight was originally delayed due to engineering issues. Jetstar says the cause of the mid air scare was a problem with one of three hydraulic systems.

The airline added that the plane could have made it safely to Bali, but the decision was made to return to Adelaide where there's better engineering support.

Just a few weeks ago, it is reported that Jetstar is under probe when a flight from Melbourne was nose-heavy at take-off because passengers were not seated properly.

The nose-heavy incident is one of the two 'serious incidents' of the airline according to Australia air safety watchdogs, The Civil Aviation Safety Authority (CASA) and the Australian Transport Safety Bureau (ATSB).

The Civil Aviation Safety Authority is looking into the incidents considering the root causes of the errors, what actions are made by Jetstar after the incidents, and the airline's compliance with regulations.

"CASA will take all appropriate actions to ensure Jetstar maintains robust and appropriate systems and processes to ensure passenger loading mistakes do not recur," a spokesman said.

The full ATSB investigation is not expected to be complete until October 2016.