It’s been a half-century since airlines started hiring women and people of color to fly passenger planes, allowing a handful of pioneering pilots into the flight deck. In the decades since, commercial aviation has grown exponentially, democratizing travel and rewiring how Americans live, work and play. But one part of the industry has remained mostly the same. Piloting is stubbornly monolithic: About 95 percent of airline pilots in the U.S. today are male. Nearly as many are white. Zakiya Percy is one of a small and growing number of people trying to change that. Ms. Percy, 29, used to dream...