American Airlines told employees Friday that all U.S.-based employees and certain international crew members must be vaccinated in light of the federal vaccine mandate.

"While we are still working through the details of the federal requirements, it is clear that team members who choose to remain unvaccinated will not be able to work at American Airlines," CEO Doug Parker and President Robert Isom wrote in a letter obtained by ABC News. 

Those who cannot be vaccinated for medical or religious reasons "can request an accommodation," they continued. 

No deadline was set.

Reuters reported Friday that the White House has pressed U.S. airline CEOs to mandate vaccines for staff by early December.

Delta Air Lines said in a statement Friday that 84% of its employees were vaccinated and the airline continues "to evaluate the administration’s plan." 

Southwest Airlines said it "continues to strongly encourage employees to receive the COVID-19 vaccine."

United Airlines has already put in place a vaccine mandate; 99.5% of its U.S.-based employees are vaccinated.

-ABC News' Mina Kaji

"Aladdin" is canceling additional Broadway performances after more COVID-19 cases were detected among the company, the show announced Friday.

The musical returned Tuesday for the first time since Broadway closed for the pandemic, though Wednesday night's performance was canceled after breakthrough COVID-19 cases among the company were confirmed. 

"Aladdin" was back Thursday night, though now all performances through Oct. 10 will be canceled after more breakthrough cases were detected Friday, the show said.

"We apologize for the disappointment and inconvenience this causes ticket holders, but we trust that audiences will agree that safety must be at the forefront of our return to Broadway," the show said in a statement on its website.

Members undergo PCR tests six times a week and are required to be vaccinated.

The deadline for New York City public school employees has passed: At least 90% of public school employees are vaccinated, including 93% of teachers and 98% of principals, according to the Department of Education. 

About 500 employees have been granted an exemption, representing .03% of the workforce.

Employees who did not provide proof of vaccination by 5 p.m. on Friday will be moved to Leave Without Pay status. Employees who get vaccinated this weekend and provide proof of vaccination on Monday may report to work as usual.

The DOE said 9,000 vaccinated substitute teachers are on standby.