The last thing Boeing needed was more trouble with its 737 MAX jet. That is exactly what it got at the start of the new year. The company had just started to regain its footing after years of tumult around the popular but troubled line of narrow-body jets when a Max 9 operated by Alaska Airlines had a structural failure Friday night. WSJ’s Alison Sider unpacks what happened. Further Reading: -Alaska Airlines Boeing Probe: What We Know  -Boeing Is Back in the Spotlight—This Time Over a MAX 9  -United, Alaska Find Loose Parts on Some Boeing 737 MAX 9 Jets  Further Listening: -The Pressure Inside Boeing  -How the Grounded Boeing Jet Shook the Airline Industry  Learn more about your ad choices. Visit megaphone.fm/adchoices