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Boeing and aviation regulators have been grappling with the aftermath of two separate bird strike incidents that caused smoke from heated oil to fill aircraft cabins.
The two incidents divided safety experts, sparked debate among US aviation safety regulators, triggered an audit of the US Federal Aviation Administration’s (FAA) actions, and even attracted an intervention from hero pilot “Sully”, famed for landing a plane in New York’s Hudson River.
Now, after nearly three years, regulators and the plane maker have settled on a fix. But it won’t be completely rolled out across the affected 737 MAX planes – some of which operate in Australia – for two years.
The saga is also a sign of how the aviation industry manages safety, particularly in an area of “fume events” – when toxic fumes enter the cabin due to the design of jet engines.
The two incidents, which both occurred in 2023, were triggered by birds that were ingested into engines, which caused “oil mist and irritating fumes” to enter the aircraft and put “aircrews and passengers at risk”, according to a US Department of Transportation report released in April.
Bird strikes “fractured the planes’ engine fan blades”, which in turn activated an engine safety feature meant to minimise damage, called the load reduction device (LRD), the report said.
When the LRD activates, “it can release over a quart [one litre] of engine oil into the plane’s environmental control systems, causing potentially toxic oil mist to enter the cockpit or cabin”, the report said.
On March 5, 2023, Southwest Airlines flight WN3923 was departing from Havana, Cuba to Fort Lauderdale, Florida when it experienced a bird strike during takeoff, which resulted “in oil mist being primarily directed into the cabin”.
On December 20, 2023, Southwest Airlines flight WN554 suffered a similar fate when its left engine struck a bird during takeoff from New Orleans, Louisiana to Tampa, Florida. In both cases, the planes landed safely.
Because most jets today rely on pressurised and heated air supplied directly through the engines (known as “bleed air”), their interiors are vulnerable to oil and additive fumes. This vulnerability alone is the source of debate between aircraft crews, plane makers and airlines.
The two incidents divided safety regulators.
In response to the incidents, one part of the FAA, the Office of Accident Investigation and Prevention, recommended alternative takeoff procedures for the 737 MAX 8, an oxygen mask for pilots that can be put on more quickly in a smoky cabin, and a software design change for the plane that uses the CFM Leap 1B engine.
But the FAA department that approves protocols for planes, the Corrective Action Review Board, instead viewed the software design change as sufficient.
The software fix will shut off engine “bleed air” in the event of the LRD kicking in, preventing toxic fumes from entering the cabin. (Bleed air supplies pressurised and heated air into the cabin).
In April 2025, the US Department of Transportation Office of Inspector General initiated a review that examined the FAA’s internal debate and conclusions. The Inspector General issued a report on the audit in April 2026. Over that period, debate about the severity of the LRD issue also unfolded.
In the US, the Air Line Pilots Association in 2025 said existing regulations were sufficient to address the problem, while a second union, the Allied Pilots Association, highlighted how an LRD-fume event could create a complex emergency for crew, according to The Seattle Times.
Captain Chesley “Sully” Sullenberger, the pilot famous for safely landing a plane with 155 passengers in the Hudson River after his plane hit a flock of birds, weighed in last year when he said: “This problem should be fixed quickly. We cannot roll the dice and take our chances in the meantime.”
A spokesman for Boeing said CFM International, the engine maker, and Boeing “have been working on a software design update”. CFM is a joint venture between GE Aerospace and Safran Aircraft Engines.
Virgin Australia, which has 19 737 MAX 8s in its fleet, said it has been engaged with CFM International and Boeing since the issue was identified and was aware of the planned software update.
Virgin stressed that safety is its highest priority, and said it continues to operate aircraft in accordance with all applicable regulatory requirements and manufacturer guidance, and with its own rigorous safety management processes.
Fiji Airways also has five Boeing 737 MAX 8s in its fleet. The company has been approached for comment.
The FAA has said that after reviewing the audit and agreeing with its conclusions, it “is committed to ensuring that Boeing and CFM International test and update affected software and that operators incorporate any necessary training so that flight crews can effectively respond to LRD activation”.
Even with a course of action decided, it will take time for the software update to be implemented and rolled out across all 737 MAX 8 aircraft.
The controversy comes as flight crews and aviation unions in Australia demand action over the suspected long-term health effects arising from such “fume events”.
Crew members and unions have linked fume events with people’s health conditions, but there remains debate over whether they form a larger pattern called “aerotoxic syndrome”.
Captain Marcus Diamond, the safety and technical manager of the Australian Federation of Air Pilots, said the group was “concerned” that the 737 MAX’s LRD, which was “designed to prevent catastrophic engine failure, creates a secondary ‘fail-to-danger’ hazard”. “Fail-to-danger” denotes when a protection system becomes inoperative if a part of it malfunctions.
Diamond said the fix wouldn’t reach the full global fleet until mid-2028, “leaving pilots to manage a failure mode that current simulators cannot even replicate”.
The safety record of Boeing’s 737 MAX has already come under scrutiny after two deadly crashes in 2019 and 2020 because of problems with its automated flight control.
Diamond said that while bird strikes were rare, they could put planes in danger. A 2024 case of a bird strike when a plane took off from Queenstown, New Zealand could have been potentially much more dangerous if the Boeing 737 model 8FE had used a LEAP engine.
More than 2000 cases of bird strikes occurred in Australia last year.
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