Investigators have disclosed that a Boeing 737-200 experienced two instances of uncontrolled pitch while in cruise during a domestic Canadian service.
The Air Inuit aircraft had been operating from Montreal to La Grande Riviere on 24 August, states Transportation Safety Board of Canada, and was about 85nm north of Montreal at the time.
Some 10min into cruise at 34,000ft with the autopilot engaged the aircraft experienced "uncommanded pitching", says the board, without elaborating as to its extent.
The pilots disengaged the autopilot and felt a vibration in the flight controls.
They re-established the aircraft at 34,000ft, requesting an altitude block from air traffic control in which to manoeuvre, before re-engaging the autopilot.
But the safety board says a second uncommanded pitching event occurred, and the crew again disengaged the autopilot before requesting a descent to 32,000ft.
Thirty-five passengers and four crew members had been on board the aircraft and one passenger was slightly injured during the event. The crew asked for an ambulance to attend at La Grande Riviere, where the jet landed safely.
Cirium fleet data shows the aircraft involved (C-GSPW) was built in 1981 and originally delivered to Pacific Western Airlines. Air Inuit purchased the jet last year.