In the wake of Southwest Airlines’ roof disaster and grounding last weekend, the Federal Aviation Administration announced Monday it will require airlines to conduct further inspections on older-model Boeing 737s. The directive will apply to about 175 aircraft, 80 of which are registered in the U.S.; most of those are operated by Southwest. Boeing said in a statement that it is cooperating with the FAA and will recommend lap-joint inspections on certain 737-series aircraft. Meanwhile, Southwest is still struggling to contain its PR nightmare. The airline canceled an additional 60 flights Monday.