From Investing.com:

United (UA) and Alaska Airlines (ALK) are affected by the FAA’s grounding of Boeing 737 MAX 9 jets after an emergency exit door fell off a plane midair. With 171 airframes affected, United Airlines and Alaska Airlines have grounded their fleets. The inspection will take 4-8 hours per plane, leading Alaska Airlines to keep the planes grounded. Southwest Airlines, operator of the 737 MAX 8, is not affected. The exit plug falling off was a part of a safety measure for high-density seating configurations, made and installed by Spirit Aerosystems (SPR).



Read more: United (UA) and Alaska Airlines most affected by 737 MAX’s latest grounding By Investing.com