United Airlines Holdings Inc. UAL -2.48% said it is providing information to health officials so they can reach passengers who might have been exposed to Covid-19 on a recent flight.

United Airlines flight 591 bound for Los Angeles from Orlando, Fla., was diverted to New Orleans on Monday for a medical emergency. A passenger was then transported to a local hospital, where he was pronounced dead.

United on Friday couldn’t confirm whether the passenger had Covid-19, but said it had received more information indicating he did have symptoms of the disease when he traveled.

The airline said it has been contacted by the Centers for Disease Control and Prevention.

“The health and safety of our employees and customers is our highest priority,” United said.

The CDC declined to say whether the passenger had Covid-19, citing privacy concerns, but said it is collecting information and following standard operating procedures to determine whether further action is needed.

Medical responders told United at the time that the passenger had suffered cardiac arrest.

As a result, the airline didn’t swap out planes but offered other passengers the choice of continuing on or taking a later flight to Los Angeles, United said Friday.

The incident ignited a social-media firestorm after another passenger posted on social media that the deceased’s wife had told emergency responders that her husband had Covid-19 symptoms.

The event highlights the difficulty of preventing potentially sick passengers from entering airports and boarding flights, where they could expose others.

United requires passengers to affirm before traveling that they haven’t tested positive for Covid-19, experienced common symptoms of the disease, or been exposed to someone who tested positive in the previous two weeks.

But it is difficult to verify that passengers answer truthfully.

A passenger who died on a Spirit Airlines SAVE -2.60% flight over the summer was later found to have Covid-19.

Flight attendants who worked on the United flight have been quarantined, a spokeswoman for their union said.

Airlines say that airplanes are uniquely safe environments due to air filtration and ventilation systems as well as strict masking requirements, and some studies have shown that the risk of transmission during flights is low.