But it has become apparent only recently, as a series of record-size corporate pension failures has put new burdens on the federal agency that insures pensions.

They said this was particularly disturbing because United's pension failure came at about the same time as the S.E.C. issued a critical report on the pension consulting business.

The accounting rules for company pensions have no direct connection with the pension-funding rules, which are now being scrutinized by Congress in light of the huge pension failure at United Airlines.

After credit balances played a key role in the $10 billion pension failure at United Airlines, a record, Congress decided to change the way the balances were handled.

Already, the agency's finances have been severely shaken by a series of large corporate bankruptcies and pension failures.

This is, in part, because of the recent high-profile pension failures at companies like United Airlines, and the questions they have raised about how best to finance retirement.

It would be the biggest pension failure since the government began insuring pensions in 1974.

The largest pension failure so far, that of Bethlehem Steel in 2002, left the government with $3.6 billion in unfunded pensions.

In most pension failures, the federal Pension Benefit Guaranty Corporation has little choice but to absorb the liabilities of the pension fund itself.

In 1974, Congress responded to an ugly string of pension failures in the auto industry by passing landmark legislation.