The WSJ reports:
Julian Walsh, director of aviation safety at the Australian Transport Safety Bureau, said an on-board electronic centralized aircraft monitoring system indicated there was "some irregularity with the elevator control system."
The aircraft departed from its normal flight at 37,000 feet, climbed 300 feet, "then as the crew were responding, the aircraft pitched down quite suddenly and rapidly," he said.
"Certainly, there was a period of time when the aircraft performed of its own accord," Mr. Walsh said.
The aircraft, built in 2003 and operated by Qantas since then, made an emergency landing at a remote airfield at Learmonth, an Australian defense force air base, near Exmouth, in Western Australia state.