Southwest Airlines Co said on Friday it has finished inspecting 115 of 128 planes that it briefly pulled out of service on Tuesday when it discovered maintenance checks were overdue, and it expects to complete the rest this weekend.
The Dallas-based carrier said the inspections, focused on the backup hydraulic systems of its Boeing Co 737-700 aircraft, have not resulted in additional repairs.
Southwest voluntarily removed the aircraft from service and disclosed the matter on Tuesday to the U.S. Federal Aviation Administration, which then said it could operate the aircraft for a maximum five days while it completed the checks.
The FAA said on Friday it does not discuss details of ongoing investigations.
“While all oversight failures are unwelcome, this scale of maintenance-related failure is hardly unique,” aviation industry consultant Robert Mann said in an email, adding that the FAA’s response on Tuesday “suggests it was not a safety-critical issue.”
The checks resulted in about 80 Southwest flight cancellations on Tuesday and about 15 cancellations on Wednesday but no others since. The airline said winter weather caused additional cancellations this week.
As of Dec. 31, Southwest operated 447 of the 737-700s, a 143-seat airplane. That variant of the venerable Boeing 737 makes up two thirds of Southwest’s fleet of 665 Boeing 737s.
Southwest Airlines has run afoul of the FAA a number of times over maintenance. Last July, the agency proposed a $12 million fine over three separate issues. Southwest has challenged the fine in federal court.
In 2008, the FAA proposed a $10.2 million fine for missing inspections for fuselage metal fatigue. It was later settled for $7.5 million.
In another incident, Southwest grounded about 80 of its older Boeing 737-300s for inspections after a roof section peeled off a 737-300 in flight near Yuma, Ariz.