American Airlines and United Airlines will begin providing workers with Johnson & Johnson's single-shot Covid-19 vaccine from tomorrow at Chicago’s O’Hare airport, according to letters sent to Chicago-based employees.

So far, U.S. airlines are not requiring employee vaccinations but are strongly encouraging them.

The industry views widespread vaccination as a key element to a recovery in travel demand that has suffered during the pandemic.

An American Airlines spokeswoman said O’Hare is the first airport where it is rolling out a limited supply of the vaccines, which will be administered by Premise Health.

United said it is working in partnership with the City of Chicago and the Chicago Department of Health.

The vaccination slots will be available on a reservation-only basis.

"Unfortunately, not having enough vaccines in circulation continues to be the biggest challenge," United said in its letter.