Aren’t maintenance protocols handled by the FAA? Otherwise it would be implied that budget carriers like Spirit or Alaska would be “less” safe (which isn’t the case AFAIK).
Maintenance protocols are a mix of manufacturer recommendations and carrier/maintenance contractor SOPs, which are then approved by the manufacturer and FAA.
In 2000, an Alaska MD-80 went down, killing all 88 onboard. The NTSB found that it was apparently due to failing to adequately lubricate the tail jackscrew, as required by manufacturer documentation, not just once, but in at least two successive scheduled maintenance periods. Also, Alaska had been increasing, with FAA approval, the period between scheduled maintenence. See https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261
Maintenance protocols are a mix of manufacturer recommendations and carrier/maintenance contractor SOPs, which are then approved by the manufacturer and FAA.