A growing number of civil aviation regulators, including the authority in Singapore, are telling their airlines that pilots should not be left alone in the cockpit.
There must always be at least two people, one of whom can be a cabin crew, in the enclosed space.
The new requirement follows the shocking revelation that a co-pilot is suspected to have locked his captain out of the cockpit and deliberately crashed a Germanwings aircraft on March 24.
All 150 people on board are presumed dead after the Airbus A-320, with German co-pilot Andreas Lubitz, 27, at the controls, crashed in the French Alps.
Could the tragedy have been averted had there been another person in the cockpit?
That is impossible to say, although it is highly unlikely that a stewardess with little, if any, understanding of flight controls, and one who was presumably not as strong as the co-pilot, could have stopped him.
Having another person in the cockpit is not a bad idea, although that is hardly the solution to the problem.
Aviation regulators, airlines and pilots all have roles to play in ensuring that flight controls do not fall into the wrong hands.
Unless there are proper checks and systems in place, and open communication among all parties, there is little hope of weeding out other pilots with depressive or sinister thoughts.
Lufthansa, which owns budget airline Germanwings, has said that Mr Lubitz took a break from flight-school training, but refused to say why.
Investigations revealed that the pilot told his flight instructors in 2009 that he suffered from "severe depression". Why and whether his condition was properly diagnosed and treated are not known.
Mental screening needs to start before a pilot is hired.
The International Civil Aviation Organisation, a United Nations arm that regulates global commercial aviation, does not set psychological standards for pilots, but only medical ones.
The onus is on local regulators to work with their airlines to incorporate psychological assessment into pre-recruitment interviews.
This is done in Singapore and many other countries, but standards vary greatly, experts said. In some parts of Asia and many developing countries in Africa and Eastern Europe, there are hardly any checks, they added.
Dr Philip J. Scarpa Jr, president of the United States-based Aerospace Medical Association, said: "Most airlines do not perform any periodic mental health assessments after an initial screening during the hiring process."
Regulators must see to it that this is done and set standards and procedures on how the assessment is to be administered.
A certified panel of doctors must be appointed and trained properly to detect and treat emotional and psychological symptoms.
An aviation medical expert, who asked not to be named, said: "I have sat through some of these assessments that are over in a matter of seconds, with the doctor simply ticking boxes. You can't help but wonder if they are even equipped to do the job."
Improvements can and should be made but regulation alone, with checks and tests conducted once, or at best twice a year, is not enough. Airlines must play a proactive role by keeping an eye on their pilots and putting in place systems and processes to encourage those with issues to seek help.
For this to work, pilots must be assured that they will not be sidelined or, worse, fired, for conditions that can be treated, for example, mild depression or stress.
Pilots, who are in the best position to look out for one another, should be trained - not typically done now - to detect signs of mental anxiety and other psychological issues.
Equally important is enhancing cockpit communication skills to break the barriers that rank and seniority can create.
"Education of the pilots, their families and others in the aviation community on what to look for in mental wellness and how to report it are important measures the airlines can take. Also, providing 'safe zones' for pilots to report any issues is important to encourage reporting," said Dr Scarpa.
What happened to Germanwings Flight 4U 9525 was unthinkable and unacceptable. While it cannot be guaranteed that a similar incident will never occur, the aviation community - regulators, airlines and pilots - must do all it can to detect pilots who are psychologically unwell.
This article was first published on April 6, 2015.
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