Are they?

Much of the work that would be done to inspect and certify the planes being manufactured was outsourced to the manufacturers to increase efficiency.

They build their planes, inspect their planes, inspect and approve modifications and major repairs to their planes, and issue their own airworthiness certificates for their planes.

For a long while, the FAA was barely even involved in rubber stamping whoever Boeing et al appointed as FAA inspectors at their plants, never mind inspecting and certifying the planes themselves—in 2016 the Transportation Department said more than 85% of the tasks associated with certification were delegated from the FAA to the manufacturer’s own inspectors. By 2018, the FAA said that Boeing was handling 96% of the certification process.

There were some reforms around 2021 (737 MAX crashes were 2018 and 2019), but they were mostly focused on improving the self inspection program, not solving the fundamental problem of having companies certify their own work.

> But it's totally incorrect to say they're an ex post facto investigations agency.

While the inspections and certifications have been delegated by the FAA and _technically_ are still done in the name of the FAA, the reality certainly looks much more like the FAA proper is only involved _after_ significant safety issues.

I really don’t think it’s quite as clear cut as you make it out to be.