Thousands of passengers who flew on commercial flights at the beginning of the year may have been exposed to COVID-19.

In a new statement, the CDC told CNN it has been informed of 1,600 flights between January and August where a traveler may have had the virus, possibly exposing 10,900 people “within a six-foot range for droplet transmission.”

“CDC identified and notified relevant health departments about these 10,900 on-board close contacts,” the statement said.

The agency said reports of confirmed coronavirus cases have surfaced from people who were identified as contacts of passengers. The CDC added that the data is inadequate due to a number of factors, including incomplete contact information, delayed warning of a sick traveler, and more. The new data arrives as airlines maintain that air travel is safe. Flying in the U.S. is currently around 30 percent of 2019’s levels.

“You are a lot safer in an airplane...than you are probably in your own home,” Nick Calio, President and CEO of Airlines for America, told CNN. “People don’t like being in a confined space, however, as opposed to being in your house, in a grocery store, in a church, in a bar or restaurant, or even a playground, you’re a lot better off.”

As an effort to boost travel, United Airlines is offering on-site coronavirus testing to customers who are flying to Hawaii and wouldn’t mind spending $250 to bypass a two-week quarantine on arrival. Bloomberg reports that Hawaii has now given travelers the option to avoid a 14-day self-isolation if they test negative within 72 hours, an amended state rule that begins on Oct. 15. The air carrier hopes that the new testing plan will encourage more international travel, which has struggled since the onset of the pandemic.