United Airlines Holdings told employees on Sunday that it expects to book US$1.5 billion less revenue in March than the same time last year, and is taking further measures to address a situation it said is getting worse.

In a memo, United said it would cut corporate officers' salaries by 50% and reduce flight capacity by about 50% in April and May, with deep capacity cuts also expected into the summer travel period.

"Even with those cuts, we're expecting load factors to drop into the 20-30% range -- and that's if things don't get worse," United Chief Executive Oscar Munoz and President Scott Kirby said in the memo.