This article was updated on Monday, December 8, 2025, to include a response from Qantas. The piece has since been updated on Tuesday, December 9, 2025, to cover a related historical case study, and Wednesday, December 10, to include expert commentary from pilots. It was originally published on Saturday, December 6, 2025.
A Qantas Boeing 737-800 aircraft departed from Canberra using take-off performance numbers based on an incorrect loadsheet after the aircraft diverted from Perth to Sydney. An input error in Qantas' departure control systems resulted in 51 passengers being listed as not onboard, which produced a calculated weight that was approximately 9,460 lbs (4,291 kg) below the aircraft's actual weight, and take-off speeds were also slightly lower than expected.
Attempts to warn the flight crew were made before this departure, but they ultimately failed. The crew later learned of this discrepancy after takeoff, and they coordinated with operations teams and placed the aircraft in a holding pattern until they were able to confirm the correct weights. The flight then continued and landed safely at Sydney Airport (SYD).
An Error Tracing Back To One Staff Mistake
The incident took place on December 1, 2024. It began when a staff member created the Canberra to Sydney additional stop and entered a configuration code for a Boeing 717 instead of the 
Boeing 737, which prompted the system to mechanically offload 11 business-class passengers and more than a dozen economy passengers that were on standby, according to reports published by the Australian Transport Safety Bureau (ATSB).
Although the code was corrected, the system did not automatically reallocate those passengers, and the flight itself was later closed using this flawed data. Load control was then issued into a load sheet that showed 51 passengers as not onboard and resulted in the massive fuel underread. Before pushback, load control was quickly identified as the problem, and teams on the ground attempted to reach the crew by phone and were unsuccessful. They were then reached out to by radio through movement control, but the message itself was not effectively delivered. The aircraft then departed, and the crew was alerted, and the correct figures were quickly verified in flight.
In the ATSB's official report, the situation was summarized as follows:
"The ATSB identified that a minor data input error resulted in an automatic, and undetected, reduction in the number of passengers allocated to the flight. This error cascaded, and erroneous passenger information was used by Qantas airport personnel to close the flight, and Qantas load control personnel to create the loadsheet"
Qantas Confirms New Measures Introduced
As airlines have various measures in place to ensure an accurate headcount on board aircraft, many have questioned how such an incident could have occurred. Although human error led to the wrong digital input in this case, flight attendants will typically perform a manual headcount during the boarding process.
Simple Flying reached out to Qantas for comment on this incident. The airline responded that it has since updated its procedures following the incident to prevent a recurrence. This includes implementing new measures for verifying headcounts, as well as ensuring vital flight information can be communicated clearly and efficiently.
A Qantas spokesperson said,
"We have introduced new measures to further strengthen our processes for verifying passenger numbers and communicating critical flight information when diversions occur. These steps are designed to enhance safety and support our teams in managing irregular operations."
An Invisible Impact For Passengers
For passengers, the most direct impact was effectively invisible in the cabin but meaningful in overall risk terms. The aircraft was rotated using inappropriate take-off speeds that were originally calculated for a significantly lighter type of aircraft. The ATSB found the incorrect weight subsequently produced speeds that were slightly lower than necessary, increasing the risk of degraded performance and unanticipated handling during take-off. The incident partially occurred because the aircraft had been forced to divert to Canberra, with the report offering the following commentary:
"After the aircraft arrived in Canberra, an error was made within the Qantas departure control system that resulted in 51 passengers being incorrectly listed as not on board the aircraft. A loadsheet was created using the incorrect passenger information that contained a weight that was 4,291 kg less than the actual weight of the aircraft. The erroneous loadsheet was issued to the flight crew who used it to make performance calculations for the take-off."
From the perspective of a traveler, this came after an already-disruptive day. The service between Perth and Sydney was diverted to Canberra due to storms, and some customers left the flight there. Once airborne, the crew received an air traffic control message that load control had to be corrected, and that the aircraft was to quickly enter a holding pattern while accurate weights were confirmed.
Despite this actually resulting in a safe outcome, these are the kinds of incidents that can erode confidence, as passenger accountability is also a major security issue; knowing who is actually onboard matters more than where they sit. Ultimately, no injuries were reported, but the event underscores why headcounts and cross-checks are reassuring.
Reputational Risk Was Greater Than Operational Risk
For Australian flag carrier Qantas, the report is actually a case study in how a single operational slip can propagate across a number of systems, like flight management, customer management, and load control. This is especially true during irregular operations like mass diversions. The ATSB concluded that airport staff attempted but failed to correct the passenger discrepancy in the system.
This led to the load control error and the need to quickly update the load sheet as concerns about data validity became very clear. Communication procedures then broke down before departure, leaving the crew unaware until after takeoff. Beyond just reputational risk, the event itself carries tangible costs, such as internal investigations, training refreshers, and process redesigns. The ATSB report did note that some changes would be made as a result, with the organization offering the following commentary:
"Qantas has amended its procedures to include a requirement for airport personnel to conduct a headcount when a passenger discrepancy is identified. Qantas has also revised its procedures for communicating critical flight information to flight crew and will implement a new procedure that allows load control personnel to contact flight crew directly via the aircraft communications addressing and reporting system when a loadsheet error is identified."
Qantas has amended its overall procedures in order to require a headcount when overall discrepancies are identified. It enables load control to contact flight crews directly when a loadsheet error is detected. This comes alongside local briefings on handovers and overall diversion handling. Passengers can expect closer scrutiny of load-control governance and accountability as weight-and-balance errors are treated seriously across the industry.
A Similar Incident Occurred 11 Years Ago, Also Involving Qantas
Interestingly, this isn't the first time that a Qantas Boeing 737 operating a domestic flight has been involved in an incident regarding incorrect weight calculations. Indeed, reporting by The Guardian in September 2014 highlighted an occurrence where, in May that year, a Qantas 737 had a 'nose heavy' takeoff due to 87 primary school children being assigned an adult weight of 87 kg when they checked in.
These children accounted for more than half of the occupants of the flight from Canberra to Perth, which also had 63 adult crew members and passengers on board. With the children seated towards the rear of the jet, the bulk of the weight was distributed towards the front, forcing the Captain to apply more pressure than usual in order to get the 737 into the air. A spokesperson for Qantas said at the time that:
"The weight of some passengers was incorrectly recorded as adults rather than children. This meant that the aircraft didn’t have the optimum configuration for takeoff, but at no stage was this a material risk to passenger safety."
Pilots' Perspectives On The Incident
Pilots' perspectives can offer further insight into such incidents. Simple Flying's very own Captain Chris explains that "weight and balance procedures, dispatch processes, [and] internal safety protocols (...) can vary quite significantly from airline to airline." However, regardless of the carrier, pilots "place a great deal of trust in dispatch, load control and traffic teams to ensure that the loadsheet data is accurate and that multiple layers of checking are in place to prevent exactly this kind of scenario."
Aviation is an industry of fine margins, where small changes can have a big effect. US-based pilot Jack Herstam explains that "when you start from an incorrect ramp weight, every weight-dependent calculation that follows is invalid," and that "just being off a few hundred pounds invalidates this computation." He adds that "when fewer people are on board, the effects of the load placement are actually amplified," with autopilot having to adjust the trim more as people walk about during cruise.
Anas Maaz, who does his flying in Asia, highlights a previous incident where weight-based inaccuracies came to the fore, namely Emirates flight 407. Here, the crew "did not realise that the weight they put in the performance software was 100,000 kg less than what was on the loadsheet." As a result, "the software calculated lower speeds and a lower thrust for takeoff," which "led to a tail strike and a subsequent investigation by the Australian authorities." You can read the ATSB report here.