The FAA ordered operators of certain Beech 1900s to visually inspect their wing spars before they resume flying after the agency received reports of cracking in the rear spar lower caps and rear spar web of two 1900Ds in August. One airplane had accumulated 19,126 service hours when its operator found the cracks in the lower aft spar cap flange. However, they extended upward into the web and ended at the lightening hole in the spar web. Similar cracking occurred on the other airplane, and analysis showed that cracks could develop in the wings of 1900s and 1900Cs as well, potentially leading to catastrophic wing failure.