Several problems need to be addressed before the FAA can authorize an inspection process and return to service.

First, why did the door fly off? Everyone is speculating that it was the loose bolts but the NTSB hasn't made an official ruling and the FAA hasn't said anything specific. Maybe the agencies, airlines, and Boeing already know the cause but the information hasn't been released to the public. Or maybe, the NTSB hasn't determined a cause. Either way, the FAA can't approve a fix until we have an official cause.

Then there's the problem of Boeing's failure to maintain the trust of the traveling public. Nobody trusts Boeing after the Max crashes, the 787 QC issues, and now the door blow-out. The politicians who run the FAA certainly won't hang their careers from Boeing's loose bolts. It wouldn't be such a big deal if it was only one aircraft with loose bolts, but both United and Alaska have found loose bolts throughout their fleets of Max 9s. Therefore, the only way the FAA could grant an easy fix is if Boeing shows that this issue is a closed case. Boeing has to pinpoint exactly how these bolts became loose, otherwise the quality control of their entire operation is suspect. Can Boeing trace this issue back to one crew, one shift, or one person? Then maybe they can claim it was a one-off training issue. Or maybe, they discover a typo in the manual, a missing page, or an incorrect diagram. Those could be valid explanations. But if the answer is "Our crews didn't properly tighten and fasten these bolts and we don't know why", then it stands to reason that Boeing's quality control is substandard and all Maxes need to go through a heavy check.

We can gripe about the FAA moving too slowly or administrators only caring about their political careers, but isn't that why we appoint independent government oversight? There must be independent, third-party oversight that is bound to the public's interest, or else complex entities like Boeing run themselves into the weeds. As somebody who operates a 737 for 600 hours a year, I welcome another set of eyes on the manufacturing process. I want someone with the power to say "no" who isn't beholden to the shareholders.