US air safety regulators have completed inspections on 40 grounded 737 MAX planes, authorities said Wednesday, in an update that did not specify when the aircraft would return to service. The inspections are part of the process the Federal Aviation Administration (FAA) is using to set protocols, before the jets are cleared for service in the aftermath of a near-catastrophic incident on an Alaska Airlines plane earlier this month. “The first 40 inspections that are part of that process are now complete, and the FAA will thoroughly review the data from them,” said the administration. In the January 5 incident, a Boeing 737 MAX operated by Alaska Airlines executed an emergency landing after a panel known as a “door plug” blew out mid-flight. There were no fatalities or serious injuries. US regulators have grounded 171 737 MAX 9 planes with the same configuration as the jet involved in the incident. The FAA has launched a safety probe into the case, the first major in-flight safety issue on a Boeing plane since fatal 2018 and 2019 737 MAX crashes. On Wednesday, the agency said its probe would extend to Boeing’s manufacturing practices and production lines. This includes those involving Spirit AeroSystems, which built the fuselage with the door plug that blew out. It added that the move shows the FAA is “bolstering its oversight of Boeing, and examining potential system change.”