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