United States commercial airline passenger traffic fell 60.1% in 2020 as the coronavirus pandemic rocked travel demand throughout the year, according to preliminary data from the U.S. Transportation Department on Tuesday.

For the year, there were 368 million passengers in total, which was down from the 922.6 million in 2019. The department stated that the previous yearly low was recorded back in 1984 at a total of 351.6 million. Moreover, U.S. domestic air travel declined by 58.7% for the year, while international travel cratered 70.4% as many airlines had to navigate various global travel restrictions.

The data is based on 22 larger carriers, including American Airlines (AAL  ), Delta Air Lines (DAL  ), Southwest Airlines (LUV  ) and United Airlines (UAL  ), that account for more than 90% of passengers.

According to Airlines for America, nine of the largest U.S. airlines lost $46 billion in pre-tax income throughout 2020, Reuters reports. The airline industry trade group added that passenger volumes may not return to pre-pandemic levels until 2023 or 2024, as the global rollout of effective vaccines are uneven and multiple new COVID variants complicate public mitigation efforts.

Harming travel demand still, the U.S. Centers for Disease Control and Prevention (C.D.C.) advised in a newly published study on Wednesday that Americans delay at least their international travel plans, due to an investigation into Minnesota residents who contracted a new highly infectious COVID variant having travel histories before displaying symptoms.

The federal health agency identified eight COVID-19 cases with the mutation first identified in the United Kingdom, known as B.1.1.7, between Dec. 18 and Jan. 11. Further investigations found that found that six of those infected had recent travel histories, either foreign or domestic, before returning to Minnesota.

According to updated C.D.C. data, there are at least 1,277 cases of B.1.1.7 infection in 42 states.

However, there is still some good news for commercial airlines as they head towards pandemic recovery. Last week, the Biden administration stated that it is not planning to require that domestic passengers show proof of a negative COVID test before departure, something airlines were fearing after the federal government mandated that international passengers test negative before take off.

"Reports that there is an intention to put in place new requirements such as testing are not accurate," White House Press Secretary Jen Psaki said in a press briefing on Friday, quoted by CNBC.