A former Chicago aviation security officer who was fired after forcibly removing a passenger off a United Airlines flight in 2017, has filed a lawsuit against the airline. In the picture, United Airlines planes sit on the tarmac at San Francisco International Airport, July 8, 2015. Getty Images/Justin Sullivan

United Airlines announced Sunday its cockpit door access information was accidentally made public but the problem had already been fixed. A flight attendant mistakenly posted information that included access codes to get in and out of a cockpit on a public website, according to reports.

The airline periodically changes codes that need to be punched into a keypad on the outside of the cockpit door to request entry into the flight deck. After the code is entered the cockpit is alerted to open the door from the inside, which also requires a specific code.

“The safety of our customers and crew is our top priority and United utilizes a number of measures to keep our flight decks secure beyond door access information,” United Airlines spokesperson Maddie King said in a statement obtained by CNN affiliate KCAL/KCBS. “In the interim, this protocol ensures our cockpits remain secure.”

Read: United Airlines Attempts Free Trip Giveaway That Quickly Backfires On Twitter

King also reportedly said the incident "was not a breach," like a hack, but did not give more information, saying the company does not discuss security procedures.

When the incident came to light Saturday, the airline sent employees a bulletin warning "flight deck access procedures may have been compromised."

The airline, which operates nearly 4,500 flights daily to more than 330 destinations around the world, did not report any flight delays or other schedule problems caused by the unusual incident.

The U.S. airlines tightened its security around cockpit access following the terrorist attacks in September 2001 and additional security was implemented after the March 2015 crash of a Germanwings jet.

The co-pilot of the Germanwings plane is believed to have deliberately crashed the plane into a French mountainside killing all 150 people on board. Authorities said at the time the suicidal co-pilot locked out the captain when he left the cockpit momentarily.

The latest incident involving United Airlines comes one month after the airline company drew widespread scrutiny for a passenger, named David Dao, who was dragged off a flight by aviation police April 9, leaving him with a concussion and two broken teeth.

United Airlines said it randomly selected Dao, along with three other passengers, to vacate the plane after no volunteers opted to give up their seats for four airline employees who needed to board the flight.

After the video of Dao being dragged off the plane went viral and the airline faced a lawsuit from the passenger, United reached a settlement for an undisclosed amount.

“Mr. Munoz said he was going to do the right thing, and he has,” one of Dao’s lawyers, Thomas Demetrio, said in a statement late last month. “In addition, United has taken full responsibility for what happened on Flight 3411, without attempting to blame others, including the City of Chicago. For this acceptance of corporate accountability, United is to be applauded.”

United Airlines became the subject of ongoing public scrutiny after multiple incidents between airline employees and passengers aboard its flights went viral.