The now-finalized rule, which was unveiled Thursday and kicks in Sept. 10, applies to certain aircraft under three Boeing 737 Max models: the 737-8, 737-9 and 737-8200. So far, no cracks have been found in these specific Max models. The Max jets have "a similar design and build process" to the older models, "making those airplanes susceptible to the same crack condition," the FAA wrote in November. The company added that it had already expanded those inspections to Max jets — and the FAA's latest directive now similarly mandates that process. Just last month, the FAA said Boeing would again be allowed to take responsibility for certifying all of its 737 Max and 787 planes.