One hundred seventy-seven passengers and crew on a Boeing flight were scared to death when the door of their plane flung open when the plane was mid-air.

The airline apologized to anyone affected and said an inspection revealed "no concerning findings."

The mid-air explosion landed Boeing (BA.N) in the situation investors and management hoped to avoid: back in the regulatory sights as it awaits clearance of new models of its best-selling MAX jet.

PHOTO | COURTESY Boeing Under Fire After Plane Door Falls Off Mid-Flight

Investigators say it's too early to tell what caused a so-called door plug to come off the side of a plane operated by one of Boeing's most devoted clients, Alaska Airlines, on Friday with 171 people on board.

On Sunday, the Federal Aviation Administration (FAA) announced that 171 Boeing MAX 9 jets BA.N would stay grounded until the FAA is satisfied that they can fly safely.

The incident occurred when Boeing and supplier Spirit AeroSystems (SPR.N), who built the panel, are dealing with persistent production problems that have impeded recovery from an earlier lengthy 737 MAX safety grounding and wider disruption from the epidemic.

PHOTO | COURTESY flight with missing door

Boeing has been under pressure to expand the MAX portfolio and close the gap with rival Airbus (AIR.PA), which has extended market share gains after two Boeing MAX disasters in 2018 and 2019 killed almost 350 people and forced the MAX to be grounded worldwide for 20 months.

The MAX's troublesome past resulted in substantial revisions to US airline rules in 2020, and the Alaska tragedy may lead authorities to take a harsher stance on other remaining issues.