One of the largest U.S. carriers, Southwest Airlines (LUV) , grounded 34 Boeing 737-700 aircraft on Thanksgiving eve after discovering shortcoming in maintenance documents. The airline claims the grounding and inspections that followed were voluntary and had minimal effect on operations.

After discovering that maintenance paperwork of some of its second-hand aircraft did not comply with the Federal Aviation Administration (FAA) safety directives, Southwest grounded the 737-700s to perform additional inspections.

The detailed visual inspections examined fuselage parts that were previously damaged and repaired, an unnamed source told Chicago Business Journal.

Southwest has confirmed to AeroTime that it indeed grounded 34 Boeing 737-700 planes for inspections on November 21, 2018. The airline notes it completed the inspections the following day, with no adverse findings.

“Last Wednesday evening, Southwest voluntarily performed additional inspections on 34 previously owned 737-700 aircraft, out of our fleet of approximately 750 aircraft, to ensure that maintenance documentation was complete and in compliance with FAA safety directives,” a statement by Southwest reads.  “There were no adverse findings, and all inspections were complete and documentation validated by Thursday." 

"Southwest completed more than 4,100 flights each day on Wednesday and Thursday, and the inspections had minimal effect on our operation. Safety is always our top priority, and we take pride in our rigorous and well-run maintenance program.”

Southwest airlines operates a fleet of 746 Boeing 737 aircraft, of which 513 are 737-700, according to data.