It seems like they grounded all of their 737 Max 9 fleet immediately after the incident. But apparently they have begun inspections and returned some of the fleet to service - https://twitter.com/jonostrower/status/1743668287106678866 and https://twitter.com/AlaskaAir/status/1743677307644944797

I can only assume major hubs have already completed inspection, because a buddy of mine flew out of Seattle on a 737 Max9 this morning. Guess I assumed inspections took longer than half a day

Supposedly the flaw exists on a section where a “false door” exists for future alterations to the exit points. Perhaps not all of their planes were built with this feature. Nothing to inspect in that case.

The number of emergency exits required depends on how many seats you cram on a plane. A Ryanair Max 9 would need that extra exit for compliance.

Do we really know the root cause this quickly?

*Slaps door of 737 MAX* this bad boy can fit so much air in it.