(Updates April 23 story to include JetBlue face mask policy)

By Tracy Rucinski and David Shepardson

April 23 (Reuters) - All United Airlines flight attendants must wear a face covering or mask while on duty starting April 24, the airline said on Thursday, one of the first major U.S. carriers to make such a requirement.

JetBlue Airways Corp started mandating face masks for flight attendants as well as other crewmembers including airport workers on April 17, a spokesman said on Friday.

The Association of Flight Attendants (AFA), whose members work for United Airlines Holdings Inc and 19 other carriers, welcomed United's move but urged Washington to require passengers to wear masks as well to protect against the spread of coronavirus on airplanes.

In an April 23 letter seen by Reuters, AFA President Sara Nelson asked the departments of Transportation and Health and Human Services to mandate masks for crew, employees and passengers; require personal protective equipment; and end all leisure travel until the coronavirus pandemic is contained.

United's move reflects airlines' evolving stance on masks for crew members as coronavirus outbreaks have spread across the world. Initially flight attendants were only allowed to wear masks on international flights to coronavirus hotspots.

U.S. pilot unions' representatives have been meeting with members of Congress to seek legislation to protect against the spread of coronavirus on airplanes, union officials said on Thursday.

"Flight crews are a unique vector for the virus, traveling all over the country. It is vital that our crews be treated as essential workers and have access to personal protection equipment and testing," said Jason Goldberg, spokesman for the Allied Pilots Association that represents American Airlines Group Inc pilots.

Major U.S. airlines have drastically scaled back flying schedules as demand has plummeted but they continue to operate domestic flights and a handful of international routes. Flights are mostly occupied by essential travelers, with business and leisure demand having virtually vanished.

Once the health crisis subsides, airline industry leaders say a recovery in demand will depend on people feeling safe.

On Monday, Canada started requiring passengers to wear a non-medical mask or face covering during the boarding process and flights.

In Europe, where travel has been more restricted due to strict lockdowns in countries like Spain, the European Commission plans to present a set of rules for the safe reopening of air travel, including social distancing. .

Some U.S. airlines have started implementing their own measures, including blocking middle seats and changing the boarding process, but have called for consistency among government requirements.

The World Health Organization's top emergencies expert Dr. Mike Ryan warned on Wednesday against opening up global travel too quickly, saying it would require "careful risk management" as societies prepare for the 'new normal' until experts better understand the virus and its transmission. (Reporting by Tracy Rucinski and David Shepardson; Editing by Richard Chang, Richard Pullin and Andrea Ricci)

Our Standards: The Thomson Reuters Trust Principles.