As passengers filed in behind them and stowed their bags that morning in Jakarta in October 2018, the Lion Air pilots completed their preflight checks amid the modern comforts of the Boeing 737 Max 8. Compared to the earlier 737, which both had flown extensively, the cabin was blissfully quiet, even during the five minutes it took for the big new engines to start up. The pilots’ seats were cushier. Four large color screens arrayed in front of them made altitude and speed readouts easier to see—nothing like the old analog dials that Boeing designers once called the “steam gauges.”

Bhavye Suneja, the captain, told his copilot, who went by the single name Harvino, that he was feeling ill, but in better health he was a sunny, life-of-the-party kind of guy. Suneja was passionate about machines; after this run he planned to fly home to New Delhi, then drive through the highlands near Nepal the next week with his wife of two years, Garima Sethi. Airlines were a family affair for the Sunejas. His mother was a manager at Air India Ltd., and his younger sister aspired to become a pilot. After flight school in California, Suneja had joined Lion Air in 2011, the same year the airline placed what was then the biggest single order in Boeing Co.’s history, a $22 billion Max purchase that co-founder Rusdi Kirana sealed with a handshake from U.S. President Barack Obama.