The flight, due for Melbourne, lost speed and altitude due to human error on January 4, 2013, according to early Australian Transport Safety Bureau findings.

According to the bureau's initial findings, the plane was forced to make a shallow descent in an attempt to gain acceleration for its flight.

The initial report said the crew, "who were experiencing a relatively high workload at the time", failed to switch the plane to a different mode of vertical climb after takeoff.

A bureau spokeswoman yesterday said the completed report would be sent to involved parties for finalisation before its publication in its regular bulletin.