EasyJet Plc was on the receiving end of an unflattering headline this week, disclosing that its average male employee’s salary is more than 50 percent higher than a female colleague’s pay. In fairness, this is explained by its pilots (mostly men) earning much more than other workers such as cabin crew (mostly women).

Still, for a company that’s been headed by a female CEO—Carolyn McCall—for the past seven years, it’s not a great look. EasyJet pointed to a 2020 target of making sure one in five of its new entrant pilots is a woman.

Of course, this isn’t an EasyJet-specific problem among airlines. As the chart below shows, the percentage of commercial pilot licenses held by females has crept up over the decades, but appears to have stalled since 2010 at below 7 percent. The figures are for the U.S., but Britain is quite similar.

Exactly why improvement is so glacial, and reversible, isn’t easy to fathom at first glance. There’s no reason women wouldn’t be as skilled in the air as men. Studies on the subject have suggested shortcomings in training programs, as well as a hard-to-shift perception among girls that this is “a man’s job” and that they’re meant to have a lifelong obsession with airplanes. One trick seems to be getting young girls interested between the ages of five and 10.

EasyJet’s target is certainly a helpful start, as it would be good to change the gender balance of an industry that looks like this:

Other businesses suffer from a lack of diversity too. Mining, for example, is a pretty male dominion. But it’s trying to change, with BHP Billiton Ltd. saying it wants an equal number of men and women workers by 2025. Plus the male/female pay gap in mining tends to be less exaggerated than for other industries.

The shortfall is smaller in mining because women workers often have similar skills to men. The hard thing for EasyJet and other airlines will be trying to get anywhere near that position.

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