DALLAS — United Airlines said Thursday it is notifying passengers who were on flights with a man later diagnosed with Ebola and telling them how to contact federal health officials.

United said it is also telling passengers that officials at the Centers for Disease Control and Prevention believe the man could not have spread the disease during the flights because he was not showing symptoms and was not yet contagious.

On Sept. 19, Thomas Eric Duncan flew from Liberia in the heart of western Africa’s Ebola outbreak zone to Belgium on a Brussels Airlines flight, according to Belgian officials.

United said it believes that Duncan flew the next day on United Flight 951 from Brussels to Dulles International Airport near Washington and connected to Flight 822 from Dulles to Dallas-Fort Worth International Airport.

United officials declined to say how many passengers were on the flights. The Brussels-to-Dulles flight was on a Boeing 777 that has 266 seats, and the flight to Dallas used an Airbus A320 with 138 seats.

In a statement, the airline said Thursday that the two planes underwent their routine overnight “thorough cleaning” after the flights, “including cleaning of lavatories and galleys with heavy-duty all-purpose cleaners and wiping tray tables and armrests with disinfectant.” It added that “we continue to clean and route the planes throughout our network as usual.”

Duncan remained in a hospital isolation ward on Thursday. According to health officials, he became sick and went to a Dallas hospital on Sept. 25, but was released, only to return by ambulance three days later and test positive for Ebola.

The airline industry and its labour unions worked Thursday to tamp down travellers’ fears about Ebola. The Air Line Pilots Association, which represents pilots at United and other carriers, said airlines have the authority under U.S. law to deny boarding to passengers who appear ill.

The union said it also had “full confidence” in procedures to contain the Ebola outbreak, including checking passengers for fever — a key symptom — at airports in western Africa.

Duncan did not have a fever when he left Liberia. But authorities there said Thursday that they will charge him with lying on a health-screening form he filled out at the airport for not disclosing that he had helped carry a woman who became ill and died of Ebola.

The disease is believed to have sickened more than 7,100 people in West Africa and killed more than 3,300, according to the World Health Organization.