Federal officials have told Southwest Airlines to fix the way it calculates the weight of luggage loaded on flights after finding frequent mistakes during a yearlong investigation.
Southwest said Tuesday it had made improvements in its methods for calculating the weight and balance of loads and that it was not facing enforcement action.
The airline said it voluntarily reported the issue to the Federal Aviation Administration last year.
The FAA investigation was first reported by the Wall Street Journal.
The newspaper said internal FAA documents showed that the Dallas airline made frequent mistakes in calculations and luggage-loading practices that could cause errors when pilots calculated their plane’s takeoff weight.
Southwest told the Associated Press that ground workers manually count and record how many bags go on each plane. The airline uses FAA-approved average weights for bags and passengers, then adds the actual weight of fuel and freight to calculate each load. Southwest said it also builds in a safety margin.
The FAA found cases in which the baggage load was more than 1,000 pounds heavier than paperwork indicated, the Journal reported.
Safety experts say pilots might respond incorrectly to an engine emergency if they have inaccurate information about the distribution of weight between front and rear cargo bays.
“It can be extremely critical,” Doug Moss, a retired United Airlines pilot, told the AP. “If the weight and balance is not calculated correctly, you could have a flight-control issue.”
Moss said pilots calculate the thrust and wing-flap settings for takeoff based on weight and other factors, and faulty data could lead pilots to put the thrust settings too low. That could be crucial if an engine fails while the plane is still climbing, he said.
An FAA spokesman said the agency opened an investigation in February 2018. Since then, he said, the FAA directed the airline to develop a comprehensive fix for the methods and processes it used to determine baggage weight.
Southwest asked the agency to close the investigation. The FAA said the agency would not do so until regulators were satisfied that Southwest’s corrections were being applied consistently.
Southwest sought to downplay the investigation, saying a so-called open letter of investigation is a common way for the FAA to discuss safety issues with an airline.
Since the investigation started, the airline’s publicity department said in a statement, “Southwest has implemented controls and enhanced procedures to address our weight and balance program concerns, and we’ve shared those measures with the FAA.”
Southwest said it believed changes it made last year “have enhanced our weight and balance program and resolved the issues that we originally reported to the FAA.”
The airline, which carries more passengers within the United States than any other, disputed an estimate that one-third of its flights took off after faulty calculations of the weight of checked bags, but it declined to give a figure.
Until last April, no passenger had died in an accident on Southwest. In that incident, a piece from a broken engine smashed into a window on the plane and a passenger was partially pulled through the broken window. The accident led to stepped-up inspection of fan blades on certain engines used by Southwest and other carriers.
The airline, however, has been fined for safety violations. Notably, Southwest agreed in 2009 to pay $7.5 million to settle FAA allegations that it operated 46 planes without performing required inspections for possible cracks in the planes’ aluminum skin.