Nitpick: Crash investigations are done by the NTSB, not the FAA.
The NTSB has no authority to enforce its recommendations. That's up to the FAA. The idea behind that is the NTSB is more likely to be impartial.
The NTSB has no authority to enforce its recommendations. That's up to the FAA. The idea behind that is the NTSB is more likely to be impartial.