By David Shepardson

WASHINGTON (Reuters) -U.S. airlines carried 66.4 million passengers in June, three times the June 2020 volume but still down 21% from pre-pandemic levels, the U.S. Transportation Department said Tuesday.

The largest 21 U.S. airlines that handle more than 90% of all U.S. traffic carried 9.2 million more passengers in June than the 57.2 million passengers transported in May. The department said June domestic passengers were down 17% while international passengers were down 45%.

The Transportation Security Administration said Tuesday that for the seven days ending Monday airline passengers screened were down 22% over the same period in 2019.

Airlines for America, an industry trade group, says U.S. airlines are operating 17% fewer domestic flights over 2019 levels and 35% fewer international flights. As a result, the group says current average domestic load factors — 89% — are identical to pre-pandemic levels.

The Biden administration has not lifted travel restrictions that bar much of the world from entering the United States, including most non-U.S citizens who have been in China, India, Iran, South Africa, Brazil, the United Kingdom and much of Europe within the last 14 days.

Last week, Southwest Airlines warned that the spread of the Delta variant of COVID-19 had hit bookings and increased cancellations, hurting its chances at profitability this quarter.

(Reporting by David Shepardson; Editing by Chizu Nomiyama and Mark Porter)