Reading the various quotes on the BBC article posted by Icare9 above, , the first question that comes to mind is : are there more bolts that need "additional tightening" or are missing anywhere else on those aircraft ? If I was the regulator I would ask for a thorough look everywhere else where there are bolts and nuts .. But that would effectively ground the aircraft for months ..And is it to be restricted to the MAX-9 ? , these " quality control failures" might exists on the other variants too..