The Federal Aviation Administration (FAA) issued two Airworthiness Directives (AD) for the Boeing 737 MAX-8 and 737 MAX-9 this week as a result of in the Lion Air crash on October 29, 2018. The crash, which resulted in the deaths of all 189 people on-board, is still being investigated by both Indonesian and Australian officials. According to Business Insider, The FAA issued the directives a day after Boeing released guidance on a potentially faulty sensor, which could result in the aircraft nosing into a dive.

Officials with the Indonesian National Transportation Safety Committee, who have been investigating the Lion Air crash, concluded that a faulty angle of attack (AOA) sensor was likely the primary cause of the incident. As such, both Boeing and the FAA have issued guidance to flight crews on what to do if the AOA sensor fails in a similar manner on their aircraft.

“This emergency AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer,” wrote the FAA in their AD.

According to the FAA, an Airworthiness Directive is a “legally enforceable regulation issued by the FAA in accordance with 14 CFR part 39 to correct an unsafe condition in a product.” The FAA has stated that compliance with this particular AD is mandatory.