http://www.cnn.com/2008/US/11/13/money.transit.agencies/index.html

The financial bailout of AIG has lowered its bond ratings, and allowed banks backing the bonds to call in their debts. $2 billion in AIG financing is owed by a number of public mass transit systems who sold their assets to AIG and leased them back. Without intervention, several may be forced to come up with hundreds of millions of dollars on very short notice- an impossible task for most municipal systems. Some are suggesting that federal guarantee of the debt can prevent the meltdown and defaults.