Some are asking whether personality tests could have prevented co-pilot Andreas Lubitz from crashing a Germanwings passenger airplane in the French Alps on March 24. But experts say many kinds of stress in the work of airline pilots can contribute to their mental health.

Dr. Andre Droog is a psychologist who has worked with KLM Royal Dutch Airlines' flight academy for 22 years. Now he is president of the European Association for Aviation Psychology, EAAP. Mr. Droog says he knows the personality type that is drawn to becoming a pilot. Usually, he says, people who want to be pilots have a good way of thinking.

"They are quite well selected and very motivated in becoming an airline pilot. They sometimes have to overcome deceptions of [failing] an exam or something but, in general they are a group of very enthusiastic people and mentally very healthy."

Mr. Droog has spent years working with pilots following training accidents caused by mechanical or pilot failure. He says the job does have factors that may impose a lot of stress on an individual.

"It's a special job. You are working at irregular times. If you have a family you are often not there and on the other hand you may be at home when everyone is at work," Mr. Droog says. "If you are flying intercontinental flights, you may build up jet lag and fatigue and of course you have to manage your life very well."

In the book "Anxiety at 35,000 Feet: An Introduction to Clinical Aerospace Psychology," author Robert Bor repeats some of these ideas. He says handling complex systems aboard an aircraft contributes to the stress of the job of a pilot.

Mr. Bor says, "These are also shift workers who do not follow the same working hours as most people and their offices are cramped flight decks at 35,000 feet in the air."

Other contributing factors to stress are regular tests. Mr. Bor says regular testing makes the pilot "subject to the close monitoring of other crew members." In other words, someone regularly watches pilots to make sure they are doing a good job. Mr. Bor says this experience is like an "incessant driving test," or a test that never ends.

Is testing the answer?

Like the U.S. Federal Aviation Administration, the European Aviation Safety Agency does not require regular psychological tests. However, these tests can be taken if examiners find cause for concern during periodic physicals, which include a discussion of mental well-being. The role of psychological tests is noted in the agencies' guidelines.

The U.N.'s International Civil Aviation Organization manual states: "Personality tests alone have not been proven to be reliable tools to predict mental disorders or to assess with any degree of certainty an applicant's suitability for an aviation career."

EAAP's Mr. Droog agrees with that assessment – a psychological test alone cannot say whether someone will be a good and responsible pilot. Mr. Droog says instead, pilots should have the opportunity to discuss their mental health many times during their careers.

"It is asking the right questions at the right time. [Pilots] have to perform during the year at least four times in a [flight] simulator for training and proficiency," Mr. Droog says.

At these times, he says, examiners giving those tests should keep an eye on possible signs of fatigue and stress. These are the critical times to talk to pilots face to face about their mental condition.

"Psychological testing is very effective in the beginning before they start training just to select the right people for the job," Mr. Droog says. "But psychological tests are not very effective in predicting life events and how people cope with them."

Incidents are rare

The Aviation Safety Network tracks information about air accidents. Before the Germanwings crash on Tuesday, the network reported that pilots had intentionally caused five crashes, killing 422 people, since 1982. Those cases involved EgyptAir, SilkAir, Royal Air Maroc, Japan Airlines and LAM Mozambique Airlines.

The aviation industry has already been making some changes to answer these events.

In Asia, psychological tests are now a common industry practice. Two of the five companies with in-flight suicides since 1982 are based in Asia.

U.S. Federal Aviation Administration rules bar anyone suffering from psychosis, severe personality disorder, manic-depressive illness or substance dependence the medical clearance to fly an airliner. Captains are required to renew their medical clearance every six months; first officers are required to renew it every year. Hundreds of people each year are refused a clearance.

European airlines are not currently required to have two crew members in the cockpit at all times, but some airlines have introduced the rule. They are doing so after it was reported that the co-pilot of the Germanwings flight had locked himself in the cockpit and did not allow the pilot to enter and take control of the aircraft. The German Aviation Association said Friday that German airlines would introduce a new rule about who must be in the cockpit.

Because of the rarity of suicide by aircraft, the Royal College of Psychiatrists in London cautions against overall judgments on depression. The college makes the point that pilots with depression have flown safely for years.

The college says pilots should have their physical and mental health tested. But, it says judgments about risk cannot be made for everyone equally. It says, "There will be pilots with experience of depression who have flown safely for decades, and assessments should be made on a case by case basis."

I'm Mario Ritter.

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psychology - n. the science or study of the mind and behavior

personality - n. the set of emotional qualities and ways of behaving that makes a person different from other people

enthusiastic - adj. feeling or showing strong excitement about something: filled with or marked by enthusiasm

depression - n. a serious medical condition in which a person feels very sad, hopeless, and unimportant and often is unable to live in a normal way

fatigue - n. the state of being very tired: extreme weariness