The Dallas-based airline has been forced to cancel hundreds of flights since last week due to mechanical problems with the fleet. Despite an "all hands on deck" staffing policy for its mechanics, the company has not been able to solve its problems.
"We require all hands on deck to address maintenance items so that we can immediately return aircraft to service and take care of our customers," it said.
On Tuesday, more than 40 aircraft had maintenance problems ̵
According to FlightAware, Southwest Airlines canceled 186 flights on Tuesday – about 4% of its business. Another 730 aircraft was delayed.
FAA started its probe in February 2018, the FAA told CNN Business on Monday.
The errors were described as "systemic and significant", and occasionally caused the reported starting weights to be 1000 pounds lower than the actual weight of the aircraft.
Southwest said in a statement to CNN Business that there is an "ongoing effort to track and voluntarily report operational data to the FAA so that we can reduce and eliminate any operational risks."
But the airline added that it has already put in place controls and procedures to deal with weight and balance problems. Southwest said it has shared these measures with the FAA.