United Airlines will require crew members to be fully vaccinated for international flight duty to certain countries with high Covid rates.
It would currently apply to flights to India, Brazil, Chile, Peru, Colombia and Argentina, United said, according to an internal memo seen by Reuters.
It could be extended to China and Taiwan based on the layover procedures there, it said.
Cabin crew will be rostered on flights to those countries as long as they are fully vaccinated from 31 July and 1 August for pilots.
"We hope that countries come off the list, rather than having to add more countries," the airline said.
The airline has also restricted unvaccinated pilots from working on routes to countries that require vaccinations for entry.
Last week United Airlines CEO Scott Kirby said the US aviation industry is facing a possible pilot shortage that could impact a prolonged travel recovery.
