Delta direct flights to Europe are already flying a much-reduced international schedule. As of May 27, it only plans to serve nine destinations in Africa, Asia, and Europe in June. The airline will offer no flights to Australia or South America. Get the best Delta deals to Europe.

The draw-down of long-haul flights by U.S. carriers comes as international traffic has been hit with country-by-country restrictions on travelers. These include outright restrictions on arrivals to mandatory quarantines or just COVID-19 testing upon landing.

Those depressed international schedules may take time to rebuild. The International air transportation Association (IATA) doesn't expect international passenger numbers to return to 2019 levels until 2023 or 2024. That’s the maximum amount as two years after domestic numbers return to pre-coronavirus levels.