The preliminary report on Air India flight AI2379 raises more questions than it answers. That is not, by itself, a criticism of an accident investigation. Preliminary reports are not intended to establish causation or apportion blame. But when an aircraft loses all three hydraulic systems in rapid succession, loses autopilot and flight-control capability, triggers a stall warning, and undergoes a significant altitude excursion, the aviation community is entitled to expect a clear account of the established facts and any immediate safety implications.
AI2379, an Airbus A320-251N, was operating from Phuket to Delhi on 4 August 2026 with 145 people on board. The aircraft was cruising at FL360 when, according to the Aircraft Accident Investigation Bureau (AAIB), the flight-control system detected a loss of Green hydraulic pressure at 04:02:43 UTC. Four seconds later, Blue and Yellow hydraulic pressures were also reported as lost. At 04:02:48, the autopilot disconnected, and a continuous, repetitive chime sounded. Three seconds later, a stall warning was triggered.
The aircraft initially climbed 372 feet above its assigned level, then descended 292 feet. The First Officer, who was Pilot Flying, attempted to control the aircraft before the Pilot-in-Command took over. (Unofficial reports indicate that the pilot was standing behind the copilot, fell during the incident, and was helped into the seat by the cabin crew. After landing, the crew assisted him off the aircraft because he could not move on his own.) Remarkably, the Blue hydraulic system recovered almost immediately, followed within seconds by Yellow and Green, with the flight-control surfaces recovering and normal aircraft operation restored. The central technical question is therefore clear: why did three normally independent hydraulic systems apparently lose pressure almost simultaneously, and why did they recover within seconds?
The preliminary report does not answer that question. Nor should it be expected to at this stage. What is harder to understand is why the report offers so little indication of what the investigation team has established about this extraordinary sequence, despite already having access to the principal sources of evidence.
The AAIB states that it recovered, downloaded, and made both the CVR and DFDR available to the investigation team. The AAIB also conducted in-person interviews with the pilots and cabin crew. It further notes that Airbus technical experts, assigned through France’s BEA, inspected the aircraft between 13 and 15 August. Investigators then removed hydraulic components and collected fluid samples for further analysis, and collected maintenance and operational records, fuel and oil samples, and ATC data.
In other words, this is not an investigation awaiting evidence. Considerable evidence was already in hand, making the lack of a meaningful technical safety assessment particularly striking. Classifying it as an accident should not be a reason to withhold established safety-relevant facts. A legitimate distinction exists between releasing factual information and prematurely declaring a probable cause. The former can support safety; the latter can prejudice an investigation.
AAIB need not—and should not—speculate publicly about the root cause while evidence is still being analysed. But it could have stated clearly what is already known. That would neither compromise the investigation nor assign blame.
Another issue that cannot be overlooked concerns what happened after the hydraulic systems recovered.
The report records that the cabin supervisor informed the cockpit of the injuries. The aircraft experienced a triple hydraulic failure, a temporary loss and recovery of flight controls, and an altitude upset. Yet the crew elected to continue to Delhi for approximately 1 hour 28 minutes rather than divert. The preliminary report records that decision but does not analyse it. This decision warrants careful professional scrutiny.
The investigation must establish precisely what the crew saw on the ECAM, which hydraulic indications remained after recovery, and what the CVR and crew interviews reveal about the crew’s assessment and decision-making.
There have also been reports of speculation about “human intervention”. The published chronology, by itself, does not establish that humans deliberately initiated the hydraulic failures. Any conclusion about crew input must be based on the correlation of control inputs, system parameters, ECAM events, warnings, and CVR evidence—not on selective leaks or anonymous briefings.
The preliminary report does not establish that the toxicology result caused, contributed to, or was related to the hydraulic failure or altitude excursion. The technical sequence remains unexplained.
What Airbus knows matters
Perhaps the most uncomfortable aspect is the apparent discrepancy between what has emerged publicly from technical sources and what has appeared in the official preliminary report. The AAIB has already confirmed Airbus's technical involvement. Yet the preliminary report makes no technical safety recommendations to Airbus or the operator regarding the apparent simultaneous loss of all three hydraulic systems.
That is not necessarily evidence of an investigative failure. A safety recommendation should be based on a sufficiently validated safety issue. If the investigation has not yet established the mechanism, an immediate fleet-wide technical recommendation may not be justified.
But this raises an important question: has the investigation established that the event was confined to VT-EXO, or has it carried out an interim fleet-risk assessment?
If the answer is yes, the aviation community should be told why no precautionary action is considered necessary. If the answer is no, that too warrants explanation.
Ultimately, a safety investigation is about learning from the last event before the next—not merely explaining it.
Transparency is itself a safety tool
At present, there is insufficient evidence to accuse AAIB of a deliberate cover-up. Such an allegation would be premature and unfair. However, the current communication strategy creates an avoidable perception of selective disclosure.
When official silence is accompanied by fragmented technical information emerging through other channels, speculation inevitably fills the vacuum. That is particularly dangerous when the event involves a modern transport aircraft apparently losing all three hydraulic systems simultaneously. AAIB’s own report states that its sole objective is to prevent future accidents and incidents, not to apportion blame or liability. That principle should extend to its communication with the aviation community. Its only substantive public statement says it is collecting evidence and that no conclusions should be drawn from isolated information. Meanwhile, detailed engineering information has emerged through the media. The consequence is perverse: the official investigator supplies less factual information than leaked Airbus and maintenance documents, leaving unofficial sources to define the public narrative.
And that creates exactly the problem we discussed previously with AI 171: confidentiality is being interpreted as silence rather than as disciplined transparency.
AI2379 presents an extraordinary technical event, a significant crew decision, and a potentially important systemic safety issue. The final cause may take months to determine. Selective leaks to the media have clouded the investigation and shaped the public narrative. There is no justification for allowing uncertainty about the cause to become uncertainty about the facts.
The aviation community does not need premature conclusions.
It needs the truth about what is already known.
Author: GR Mohan
