Amid scrutiny, Boeing promises more quality checks. But is it enough?

the Federal Aviation Administration has grounded 171 of the 737 Max 9 planes in the United States, as it conducts an audit of the Boeing's production line. FAA officials have said the regulator is considering adding an independent third-party inspector to oversee Boeing inspections and quality. (AP)

After a door plug blew off an Alaska Airlines Boeing 737 Max 9 jet mid-flight, leaving a hole in the side of the plane and forcing an emergency landing, the airplane maker has been scrambling to restore confidence in the company's grounded aircrafts and get them back in the air.

Among other changes, the company is adding new quality inspections to 737 production lines at Boeing factories as well as Boeing's third party parts supplier, Spirit AeroSystems, according to a Monday statement. Spirit AeroSystems is the company that made the door plug involved in the incident on Jan. 5.