PORTLAND, OR. – (KGMI.com) United Airlines says it has found loose bolts and other “installation issues” on a part of some Boeing 737 Max 9 jets that were inspected after a mid-flight blowout on a similar Alaska Airlines jet Friday.

The inspections are focused on plugs used to seal an area set aside for extra emergency doors that are not required on United and Alaska Max 9s.

That plug is the part that blew off the Alaska plane as it cruised 16,000 feet over Oregon.

The FAA grounded all Max 9s operated by Alaska and United and some flown by foreign airlines after the terrifying incident on Friday night.

The Boeing jetliner that suffered the blowout had cabin pressurization warnings go off on three previous flights.

But the National Transportation Safety Board says it’s not sure that the area of the aircraft that failed was related to the pressurization issues.