Southwest Airlines (WN, Dallas Love Field) has accelerated the planned inspections of second-hand B737-700s it acquired between 2013 and 2017 after the Federal Aviation Administration expressed concerns about the low-cost carrier potentially operating aircraft with undocumented repairs.

"Southwest Airlines accelerated the timeline for completing the remaining inspections by five months - from July 1, 2020 to January 31, 2020. In response, the FAA communicated to congressional committees of jurisdiction that it believes Southwest Airlines is taking the FAA's concerns seriously and that revoking the airworthiness certificates of the uninspected aircraft is unnecessary," the US Senate Committee on Commerce, Science, and Transportation said in a newly related fact sheet related to the case.

According to the carrier's statement provided to Reuters, it will accelerate the inspections of 38 aircraft which were initially due for checks by July 1, 2020.

The case relates to a total of 88 aircraft that Southwest Airlines acquired from foreign carriers. The carrier used its Delegated Airworthiness Representatives' authority to issue these 88 aircraft airworthiness certificates after multiple contractors conducted the review of the aircraft's maintenance records.

However, in March 2018 an FAA inspector discovered discrepancies in the records of some of these 88 aircraft during routine inspections. A subsequent full review found 360 previously unknown major repairs conducted on the aircraft prior to their acquisition by Southwest. The FAA allowed Southwest to continue operations of these aircraft but mandated inspections by July 1, 2020.

The inspector who discovered the discrepancies disagreed with the FAA's decision to allow operating the aircraft until inspections were conducted. Acting upon the inspector's internal report, the director of FAA's Office of Audit and Evaluation Clay Foushee suggested grounding the aircraft on October 24, 2019.

Meanwhile, Southwest itself reported on October 4 that out of 39 already inspected aircraft, 24 were found to have undocumented repairs that were nonconforming to compliance requirements. In late October, the FAA expressed concern about both the speed with which Southwest Airlines was completing the maintenance checks and the potential for the remaining 49 aircraft to require the same immediate maintenance to come into compliance.

The FAA whistleblowers also pointed out to the "alarmingly insufficient" level of initial reviews performed by Southwest's contractors. Allegedly, one of the contractors did not even translate documentation into English.

So far, Southwest Airlines completed inspections of 41 aircraft, leaving 47 yet to be inspected.

According to the ch-aviation fleets advanced module, Southwest Airlines currently operates 511 B737-700s and 207 B737-800s. Out of these, 150 -700s were acquired from other airlines, including 51 taken over from AirTran Airways (FL, Atlanta Hartsfield Jackson) after Southwest took over the airline. Three -700s were acquired from Alaska Airlines (AS, Seattle Tacoma Int'l) and one from Eastwind Airlines (W9, Philadelphia Int'l), with the remainder previously operated outside of the United States. All of the carrier's -800 have been delivered to Southwest directly from Boeing.