A Federal Aviation Administration official wrote a memo last month saying that Southwest Airlines Co. should ground 49 of its airliners because repairs were performed that don't meet legal standards.
There is "a high likelihood of a violation of a regulation, order or standard" of the FAA, and the U.S. regulator needs to take immediate action to revoke the certification of the planes, said H. Clayton Foushee, the agency's director of the Office of Audit and Evaluation. The Oct. 24 letter was released Monday by the Senate.
The FAA wrote to Southwest days later ordering the airline to speed up inspections of the 737 NG planes, which were previously owned by foreign carriers. But it has stopped short of requiring that the planes be grounded. The agency said in a statement that a risk assessment had concluded the airline had taken appropriate measures.