United Airlines will begin collecting contact information from passengers when they check in as part of an effort by the Centers for Disease Control and Prevention to better track spread of the coronavirus.

Starting this week, passengers traveling to the U.S. on international flights will be asked to voluntarily provide their email address, phone number and an address where they can be reached, the Chicago-based carrier said Wednesday. United will ask those flying domestically and to international destinations to provide the information in the coming weeks.

Giving the CDC immediate access to more complete contact information for passengers is expected to help public health officials follow up more quickly with people who have been potentially exposed to COVID-19 while flying.

“Initiatives like testing and contact tracing will play a significant role in slowing the spread of COVID-19 until a vaccine is widely available,” United’s Chief Customer Officer Toby Enqvist said in a news release.

Delta Air Lines became the first U.S. airline to work with the CDC on contract tracing earlier this month, according to a news release. The airline began collecting contact information from passengers traveling to the U.S. on international flights Tuesday.

Customers can opt into United’s contact tracing program using the airline’s mobile app, by going to the website or when they check in at the airport.