In 2009, Colgan Air 3407 crashed while landing at Buffalo, N.Y., killing all 49 people on board. An investigation determined that leading up to the crash, pilot performance was likely impaired by fatigue: a finding that came as no surprise to safety advocates who had long recognized its dangers.

In the 1980s, NASA dedicated an entire research program to understanding fatigue. The effort was groundbreaking for its time, as researchers examined the influence of sleep loss and interruption on brain function, muscle activity and alertness. Those measures were used to paint a snapshot of fatigue, based on when pilots flew, how long they flew and how much rest they had obtained before the flight. The program laid the critical groundwork for the development of the fatigue management standards used today.

However, these standards have faced stiff resistance from air carriers. For example, when the FAA recently announced limits on night flying, cargo carriers successfully lobbied for exclusion because of the “unreasonable” $550 million price tag. That decision appalled many. Robert Travis, president of the Independent Pilots Association, notes that it was not the government's intent to address the important issue of pilot fatigue “only if the price is right.” Perhaps not, but costs are precisely why fatigue management standards are opposed; they reduce profit margins by limiting how much productivity can be squeezed out of workers. And in a climate of fierce economic competition, airlines hesitate to pass on any additional costs to customers.

Unsurprisingly, safety advocates lauded the FAA rule. Nico Voorbach, president of the European Cockpit Association, says that unlike European governments, the U.S. has taken a decisive step toward what a wide body of scientific medical research recommends to be safe. But does science really support the assertion that fatigue reduces safety? And more important, does the public value efforts to manage fatigue?

Justification of fatigue management standards is based on more than three decades of scientific research. Yet although these studies have examined the impact of fatigue on everything from oxygen levels in the brain to short-term memory, a mere handful have examined how fatigue affects a pilot's flying ability. This is surprising because today's technology allows monitoring of every facet of the job. Was too little engine power used during takeoff? Was too much brake pressure applied during landing? If so, the system has a record of it. And if a fatigued pilot is doing something dangerous, we should know about it.

Anecdotes tell of sleepy captains forgetting to extend flaps before takeoff to overworked first officers nodding off at the controls while in command. In one recent case, a fatigued Air Canada pilot sent an airliner into a 400-ft. dive over the North Atlantic after mistaking the planet Venus for another aircraft on a collision course. Sixteen passengers were seriously injured. However, standards must be based on methodologically sound research, not anecdotes, and as yet, the relevant research is lacking.

Whether the public values such efforts is a difficult question. A recent public opinion survey found that 82% of passengers rank fatigue as their most important air travel concern. But are their concerns reflected by their behavior? In 2006, a British television station used secret film to substantiate allegations that Ryanair forced its pilots to work excessively fatiguing schedules, flying multiple consecutive flights a day through congested airspace with few opportunities for rest.

How did customers respond? By helping Ryanair grow from a tiny, impoverished Irish carrier to Europe's largest airline, and a very profitable one at a time when some of its competitors are facing loses and insolvency. The secret to Ryanair's success is simple: cheap fares. Clearly, public concerns over fatigue are tempered by the prospect of flying from Brussels to Barcelona for €14.99 ($21).

Ryanair is hardly unique among its peers when it comes to reports of fatigue. But its remarkable growth despite such reports forces us to face a harsh reality: If passengers want air travel to be safe, they must be willing to pay for it.

Ashley Nunes is a principal scientist at ISA Software, a company that develops simulation tools and analytical software for aviation and air traffic system modeling. He is based in Paris.