U.S. passenger airlines carried 670.4 million passengers in 2021, up 83% over 2020 levels but still down significantly from pre-pandemic levels, the Transportation Department said on Monday.

The department in preliminary data said airlines carried 303.6 million more passengers in 2021 but 245.9 million fewer, or 27%, than in 2019. In 2019, domestic flights accounted for 88% of all passengers, while domestic trips accounted for 91% of all passengers in 2021, and international flights accounted for 9%.