Delta Air Lines said on Thursday it expects a cash burn of about $12 million to $14 million per day in the fourth quarter as slowing demand amid a spike in COVID-19 cases adds about $2 million per day to its burn rate.

"We've seen some slowing of demand and forward bookings as COVID cases have risen across the U.S," Chief Executive Ed Bastian said in a memo to employees.

The carrier said fourth-quarter revenue could fall to 30% of 2019 levels, which was $11.44 billion.

Meanwhile, Delta is partnering with the Centers for Disease Control and Prevention to keep international customers informed of potential COVID-19 exposure through contact tracing.

The airline said it will ask customers traveling to the United States from an international location to voluntarily provide five pieces of data to aid contact tracing and public health follow-up efforts beginning Dec. 15.

Earlier in the day, Spirit Airlines said it expects its load factor for the fourth quarter to average about 70%, despite the slowdown in demand due to the COVID-19 pandemic.