The share of recent loans backed by the Federal Housing Administration that are seriously delinquent fell in February to the lowest point since last summer, reversing an alarming increase in the agency's default rate. About 4.8% of FHA-backed loans made in the two years ended February 28 were at least three months late, down from 5% in the two-year period ended January 31, according to the agency's most recent public data. About 154,000 loans were seriously behind and another 8,500 had gone bad, requiring the agency to pay claims to lenders. The agency's default and claims rate climbed April through November before leveling off in December and January and starting to decline in February, the data show. The FHA played a critical role in propping up the housing market by insuring lenders it works with against losses after the mortgage market unraveled. But the agency's default rate shot up as its loan volume expanded, depleting its cash reserves to dangerously low levels and raising concerns about a possible taxpayer-funded bailout.