United Airlines said on Wednesday that it plans to cut more than 16000 jobs as early as next month after federal anti-epidemic aid is exhausted.

Many of these involuntary layoffs are without pay, meaning they can be recalled if travel demand picks up. The job cuts account for nearly 17 per cent of United's workforce.

But the figure is well below the 36000 job cuts that United warned in July as thousands of employees accepted voluntary buyout contracts, early retirement plans and other forms of temporary leave.

United Airlines said in a staff memo: "the impact of the COVID-19 epidemic on us is deeper and longer than almost any expert predicted. In an environment where travel demand is so low, United cannot continue to provide staffing far beyond our flight schedule."

Airline unions and executives have urged Congress to provide an additional $25 billion in federal aid, but lawmakers have yet to approve a new national epidemic relief plan, which may include aid to airlines.

The initial grant to airlines was part of a $2.2 trillion anti-epidemic relief program in March, requiring airlines to ban layoffs or pay cuts until Sept. 30.

Providing wage support can help airlines cope with the decline in travel demand, according to federal government data, but travel demand has been hovering around 30% of last year's levels affected by the epidemic, and airlines are trying to reduce the number of employees.