KEY TAKEAWAYSBoeing has found cracks in the structure of its 777X jetliner in initial test flights, another mishap for the carrier this year.The company is grounding its 777X test fleet after an inspection showed the failure of a key engine mounting structure.Boeing shares are down more than 30% this year as the airplane maker grapples with a series of setbacks since a door plug detached during an Alaska Airlines flight in January. Boeing (BA) has found cracks in the structure of its 777X jetliner in initia ...