United Airlines plans to lay off about 30 percent of its managers as the coronavirus slows global air travel sharply, according to a document seen by AFP on Tuesday.

The airline also is planning to eliminate thousands of pilot positions, the US carrier's operations director Greg Hart said in a memo, while the cuts amid executives would amount to about 3,450 jobs.

"Unfortunately, in the coming weeks and months we expect to be faced with the need to right size our frontline workforce to match demand," Hart wrote, without giving further details.

A source familiar with the matter said a third of United's 12,250 pilots may have to leave the company.

Other airlines, including Delta, also have warned of coming job cuts.

United received about $5 billion from the US government as part of a massive $2.2 trillion stimulus package intended to help industries hit by the coronavirus downturn.

More US airlines are warning they will have to reduce staff
More US airlines are warning they will have to reduce staff GETTY / Michael Ciaglo

Under the terms of the funding, the airline must not make layoffs before September 30, but the company has made clear that once that date passes, cuts are necessary.

"Even with a federal government grant that covers a portion of our payroll expense through September 30, we anticipate spending billions of dollars more than we take in for the next several months, while continuing to employ 100% of our workforce. That's not sustainable for any company," Hart wrote in his memo.

In another memo, United's human resources director Kate Gebo said workers facing layoff will be informed by mid-July.

Employees leaving voluntarily will receive a severance package, part of which will be in cash, but that offer will not be available after October 1, she said.

The company has been forced to cancel 90 percent of its flights, and Gebo encouraged executives to take 20 days of unpaid leave between mid-May and the end of September, and asked some to work four-day weeks.

"The reality we are faced with, especially heading into what would normally be our busiest time of year, is daunting to say the least," Gebo said.