One man who heard the cockpit voice recording from the doomed Germanwings Airbus A320 described noticing the personality of the copilot, Andreas Lubitz, undergoing a subtle change shortly before he apparently locked his captain out of the cockpit. Whereas he had sounded "normal" after take-off, his replies to his captain later became "laconic", Marseilles prosecutor Brice Robin told a press conference yesterday.
Perhaps with the benefit of hindsight, psychiatrists might be able to explain his change of demeanour but there appears to have been little else to suggest beforehand that flight 4U9525 was about to pass into the control of a maniac.
Lubitz was otherwise in every respect, it seems, a normal, everyday guy with no problems.
This poses a serious dilemma for airlines and regulators alike. Anti
-terrorism and other aviation security measures are working extremely well but they have failed to cope with what is effectively an enemy within, the rogue pilot.
Pilots undergo a battery of personality and psychological tests before they are hired but, it now appears, they are not enough.
Despite the seismic shock generated by the revelation that Lubitz appears to have flown his aircraft into the ground, we cannot say we have not been warned. This has happened several times before, killing hundreds.
Aviation safety experts will probably admit they cannot rule out the possibility that suicidal pilots may have been responsible for some otherwise inexplicable previous air disasters.
In 1982, a Japanese DC-8 captain
Seiji Katagiri suddenly grabbed the engine controls of his jet and applied reverse thrust on two of its four engines, throwing it out of control. Two crew members struggled with him and subdued him but not before the aircraft crash-landed near the airport, killing 24 of the 166 aboard. Katagiri told rescuers he was an office worker, not a pilot. He was later found to be insane.
Capt Tsu Way Ming was possibly Katagiri's Indonesian counterpart. In 1996 he pushed his Silk Air Boeing 737 to a fatal dive into a river, killing all 104 aboard. It later emerged he had massive debts after losing heavily on the stock market.
Two days before the accident he bought a $600,000 insurance policy. The US National Transportation Safety Board (NTSB) declared the crash the result of a murder/suicide although Indonesian authorities refused to accept this verdict.
Gameel Al-Batouti was the first officer blamed for flying Egyptair flight 990 into the Atlantic en route to Cairo from New York in October 1999, resulting in the death of all 217 aboard. He had invited his colleagues to take a break before carrying out what US investigators called a murder/ suicide.
The Egyptian authorities rejected this finding, saying it had resulted from a flawed elevator, although the NTSB said the flight recorder’s trace of the aircraft’s final moments did not match the Egyptian scenario.
Younes Khayati, the pilot of a Royal Air Maroc turboprop, was blamed for deliberately crashing his flight into the Mediterranean killing all 40 passengers, plus the crew, in 1994. Among the dead was a Kuwaiti prince.
It might not be fanciful to suggest that the 2013 crash of Lam Mozambique Airlines flight 470 killing all 33 aboard could have provided the template for this week's Germanwings disaster.
The copilot was locked out of the cockpit after taking a toilet break and the cockpit voice recording contains the sounds of the copilot banging on the door demanding to be allowed back in. Investigators suggested Capt Herminio dos Santos Fernandes crashed the jet by altering autopilot altitude settings.
Might a similar modus operandi have been at play aboard the Germanwings jet?
This disaster will inevitably lead to calls for cockpit door security procedures to be revised but any measure giving pilots and/or cabin crew easier access to a locked cabin will also be viewed as making the same task easier for terrorists.
And, might Robin, the French prosecutor, be ultimately proved wrong in his assessment that the cockpit voice recording conclusively demonstrated that a crime had been committed?
The FBI muscled in on the investigation of two major US air disasters after declaring them to be the result of bomb attacks only to later admit it had been wrong. Investigations into the 1994 fatal crash of a USAir Boeing 737 near Pittsburgh in 1994 subsequently found a flawed rudder control, not a bomb, was responsible, while TWA flight 800 was later found to have been brought down by a fuel tank explosion, not a terrorist's bomb, off the coast of New York in 1996.
Robin is assuming that the reason the Germanwings captain could not gain readmittance to the flight deck was because Lubitz overrode the emergency unlocking mechanism.
However, supposing it later emerges that this mechanism was somehow faulty and that the reason Lubitz ignored both his pleas and radio calls from air traffic controllers was because he was unconscious?
Despite the importance of a crashed aircraft’s black boxes, valuable clues often emerge from a painstaking examination of the wreckage and that should be allowed to continue in a methodical fashion, despite the otherwise plausible suspicions of magistrates.
Remember also that the disappearance of Malaysian flight 370 in March last year was initially blamed on the murder/suicide of its captain, an accusation now seemingly retracted by the Malaysian authorities.
Gerry Byrne is the author of Flight 27: Anatomy of an Air Disaster, published by Copernicus Books, New York