Southwest Airlines (LUV  ) is staring down a potential fine of $3.9 million after the FAA found that the airline had flown over 20,000 flights with incorrect weight and balance data.

The Federal Aviation Administration said in a statement issued on Friday that the agency was proposing a fine for Southwest for allegedly operating flights with incorrect data, which runs contrary to FAA regulations and could pose a danger to passengers. In the statement, the FAA says that Southwest "operated 44 aircraft on a total of 21,505 flights with incorrect operational empty weights, and center of gravity or moment data." This is not the first trouble Southwest has run into with this particular issue; the airline is actually under investigation for separate incidents involving weight and balance data.

FAA regulations are in place regarding weight and balance data because of the dangers posed by incorrect weight distribution. Weight calculations ensure that a plane is not too overloaded before attempting to fly; calculations dictate how many passengers a plane may carry along with fuel and cargo. Additionally, weight must be balanced to keep the plane's center of gravity from being too skewed in one direction.

The issues may stem from Southwest's previous antiquated practice of manually counting and weighing passenger bags, which leaves room for human error. The FAA's investigation into Southwest's weight and balance practices prompted the carrier to switch to a computerized method of scanning bags that most airlines currently use, and generally to refine its weight calculation methods to avoid further mishaps.

Southwest has acknowledged the allegations and stated that the issues had been resolved, stating, "The proposed FAA Civil Penalty pertains to data processing issues that occurred while transferring aircraft weight information from one Southwest computer system to other computer systems in the spring of 2018. The issues were identified and