Nearly 13,000 American Airlines employees are at risk of furlough starting April 1 when the U.S. aid package for airline workers is set to expire.
The airline blames a travel slump on slow vaccine rollouts and new international COVID-19 restrictions.
In a company-wide memo, CEO Doug Parker and President Robert Isom told employees: "We are nearly five weeks in 2021 and unfortunately, we find ourselves in a situation similar to much of 2020."
Furlough warnings went to over 1,800 pilots and 4,000 flight attendants.
Nineteen thousand American Airlines workers were already furloughed when the first federal payout of the global health crisis expired in October.
They were recalled in December when the latest $15 billion aid package was passed, enough to pay their incomes through March, but as the April deadline approaches, aviation unions are pushing for another $15 billion to protect jobs through the summer.
United Airlines is also sending a fresh round of furlough warnings to 14,000 employees, as they're required by law to inform employees who might lose their jobs within 60 days.
Meanwhile, Delta and Southwest have mostly avoided layoffs through voluntary leave programs.