Access codes for United Airlines airplane cockpits may have been published online, the company said Monday, a day after a report about an “accidental” breach caused concerns about air security. Maddie King, a spokewoman for the airline, said additional measures will be taken to ensure security on flights, though she did not elaborate on them. She neither confirmed nor denied a report by The Wall Street Journal on Sunday that said a flight attendant had accidentally published the confidential codes on a public website. According to that report, the airline’s pilots were warned about the potential security risk. “We are working to resolve this issue as soon as possible,” King told Reuters. U.S. airlines have placed special emphasis on cockpit security since the Sept. 11, 2001, terror attacks, when hijackers crashed planes into the World Trade Center and Pentagon.