Spirit AeroSystems was a company little-known outside the aviation industry until January this year.Then, however, the fuselage maker was flung into the spotlight when a Boeing 737 MAX jet operated by Alaska Airlines suffered a mid-air blow-out of a door plug. Spirit, whose operation in Wichita, Kansas, had made the fuselage for the jet, saw its shares plunge by as much as 20% and found the quality of its work coming under heavy scrutiny as Boeing scrambled to convince regulators and customers that its airc ...