Andreas Lubitz, the co-pilot who last week steered a Germanwings flight into a mountainside, had a history of depression so debilitating that he left his pilot training program for six months in the late 2000s, according to Germany's Bild newspaper.

When he was ready to return, he had to pass a battery of psychological tests required for pilot certification, as well as another series of tests that were a prerequisite for his job at Lufthansa, which owns Germanwings. But in all likelihood, that was the last time Lubitz's employer or government subjected him to a formal psychological evaluation.

In hindsight, that might seem an instance of negligence. But it's sadly representative of the broader problems with how the aviation industry, and especially budget carriers like Germanwings, have failed to prioritize pilots' psychological health.

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Commercial flying, as anyone who steps onto a plane knows, is an increasingly stressful activity for passengers. But the same goes for flight crew. In recent years, crews have often had to sacrifice compensation and time off, even as their workloads have increased. Of course, airline pilots aren't alone in facing such job-related stresses. But they are unique in their responsibility for multi-million dollar vehicles and the hundreds of people they carry.

Arguably, no group of pilots has been under greater stress in recent years than those flying for budget carriers. The business model is simple: provide cheap fares on the back of ruthless cost-cutting. Much of that cost-cutting falls on the backs of crew, whether in the form of reduced benefits or requirements that planes be prepared for takeoff as quickly as possible after landing. Though no study has taken a look at the physical and psychiatric effects of low-cost piloting, a 2006 study concluded that "identifiable fatigue problems are reported by short-haul pilots," including those at low-cost carriers. Fatigue can directly impair job performance. As countless studies have shown, it can also trigger a range of psychological illnesses.

So who would want to work under the conditions set by budget airlines? Any pilot desperate for a job -- of which there are plenty, thanks to the crippling levels of debt that aspiring pilots often rack up while studying at expensive flight training programs. As The Atlantic put it last year, pilots regularly take on "$200,000 in debt for a job that pays $22,914 per year, to start." Budget carriers have a reputation for exploiting this desperation. Last month, Bloomberg reported that low-cost carriers are "chasing the lowest pay and most relaxed work rules for pilots," which creates uncomfortable questions about "safety oversight." Ideally, the International Civil Aviation Organization, the United Nations' aviation agency, would interrupt this race to the bottom by setting psychological safety standards for pilots. But ICAO has long dismissed the utility of psychological testing. In its Manual of Civil Aviation Medicine, it said such tests are "rarely of value." As a result, each country sets its own standards for how pilots should be evaluated psychologically once they've been certified and hired -- and those standards tend to be lax. Some countries, including the United States, don't mandate any formal psychological evaluations for active pilots. Rather, they roll them into a pilot's regularly scheduled medical examinations.

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The U.S. Federal Aviation Administration's guidelines for performing such check-ups are underwhelming. Physicians are asked to draw"a general impression of the emotional stability and mental state of the applicant." If something seems off, the physician can recommend a formal psychological evaluation that - - if failed -- can lead to serious penalties, including suspension. For pilots suffering from depression or other mental illnesses, this provides a strong incentive to lie, and a disincentive to seek treatment.

A better system would require pilots to undergo more rigorous and regular psychological screenings performed by psychologists, not physicians. And during those tests, pilots should be assured that they have the option of seeking treatment without having to fear losing their jobs. As one anonymous pilot quoted by The Atlantic's James Fallows on Friday puts it: "The aeromedical system could start with the premise that their job is not to keep people out of the cockpit, but to put them in one safely." For now, we can't say if additional screening would have flagged Lubitz. But even if it failed, the information gleaned from widespread screening would provide airlines and regulators with a far better understanding of their pilots. It might even encourage them to take steps to improve their mental health.

Adam Minter is based in Asia, where he covers politics, culture, business and junk.