Airline companies say COVID-19 vaccines may become a requirement for international travelers. The requirement could help air carriers increase international travel after worldwide slowdowns caused by the coronavirus crisis. Promising news about vaccine development has given airlines and nations hope that they may soon be able to restart suspended flights. But some countries, especially in Asia and the Pacific, do not want their hard-fought gains against the virus to disappear. Alan Joyce is head of Australia’s largest airline, Qantas. He said that once a COVID-19 vaccine is widely available, his carrier will likely require passengers to use it before they leave or land in Australia. Joyce said he has been talking to officials at other airlines around the world about the possibility of creating a “vaccination passport” for international travelers.