Canadian investigators believe wake turbulence caused control problems on a WestJet Boeing 737-800 just after it lifted off from Los Angeles.
The aircraft experienced turbulence, from a departing Airbus A321, as it climbed through 500-900ft during a service to Calgary on 24 July.
Transportation Safety Board of Canada says, in an incident bulletin, that flight WS1513 took off from runway 24L.
The wake turbulence was strong enough to cause an uncommanded roll and disconnection of the autopilot, it adds.
"Required spacing between the A321 and [the 737] had been correctly applied by air traffic control," it says. The crew took manual control and corrected the roll, and the flight proceeded without further incident.
None of the 137 passengers and six crew members on board the 737 was injured. Transportation Safety Board of Canada has not publicly identified the operator of the A321.