The Australian authorities have confirmed in a report that the omission of some mandatory pre-departure checks was the reason why Malaysia Airlines flight MH134 had to turn back and perform an emergency landing at the Brisbane Airport on July 18.
The crew did not notice that the plane's pitot probes - which measure air pressure to assess speed - were covered, resulting in an air-speed indication failure, according to a preliminary report published by the Australian Transport Safety Bureau (ATSB) on Thursday (Aug 30).
The carrier had earlier said on July 19 that the incident "was due to an unexpected technical issue that occurred after take-off".
The Airbus A330-300 left Brisbane at 11.18pm local time and was due to arrive in Kuala Lumpur at 5.50am local time, but had to turn back and land. No one was injured in the incident after it landed back at Brisbane Airport at 12.34am.
However, the main runway had to be closed for 90 minutes, according to newspaper The Australian. The aircraft eventually had to be towed to the gate.
It added that Brisbane Airport requires pitot probes be covered due to wasps building nests in the openings and blocking them.
The red pitot probe covers usually have a long tag labelled with the words "remove before flight".
The report noted that the covers were not detected by the airlines' maintenance engineer, the captain and ground handlers during separate external aircraft inspections and pushback, which is when the aircraft is pushed backwards away from an airport gate.
The flight crew and maintenance engineer said in the report that they do not routinely use pitot probe covers on a turnaround and did not normally fly to airports where its use was standard.
It was revealed in security video recordings that the covers were not used in Malaysia Airlines' three previous turnarounds.
ATSB chief commissioner Greg Hood told The Australian that the incident is a serious one and added that the investigation is ongoing.
"We will be focusing specifically on the procedures for flight crew and ground crew, in relation to the pre-flight checks for the aircraft and also the cockpit warning systems received by the flight crew as they accelerated down Runway 01," he said.