The US Treasury Department says it has disbursed $US2.9 billion ($A4.56 billion) in payroll assistance to 54 smaller passenger carriers and two major passenger airlines, while it finalised grant agreements with six major airlines.

The Treasury is initially giving major airlines 50 per cent of funds awarded and releasing the remainder in a series of payments.

In total, Treasury is awarding US passenger airlines $US25 billion in funds earmarked for payroll costs.

Airlines must repay 30 per cent of the funds in low-interest loans and grant Treasury warrants equal to 10 per cent of the loan amount.

Treasury said Monday it has finalised grant agreements with Allegiant Air, American Airlines, Delta Air Lines , Southwest Airlines, Spirit Airlines, and United Airlines.

Air carriers have been devastated by the coronavirus pandemic and seen US travel demand fall by 95 per cent.