They may not be putting any money up front but if UAL defalts the Government Guarantees that any loss the lender has they will reimbuse them from Government funds to compensate them for any loss incurred. Up to the amount of the original loan.
Any one who has purchased a house with FHA financing has also had a governmet backed loan. The Government guarantees for an insurance premium paid by the Buyer of 1/2 % added on to their loan interest, plus aprox. 1% as an up front fee of the loan amount. If the Lender has to forclose the Government reimburses the Lender for all losses up to 20% of the loan amount.