They worry, too, that employers that are around may choose to dump older workers for younger ones, thus avoiding the big payments, or to terminate their pension plans.

When asked to do so, they usually complain that such a calculation is inappropriate because they have no intention of terminating their pension plans.

No other airline has terminated all its pension plans, except in cases of liquidation, where the airline itself was going out of existence.

For companies that terminate their pension plans, such gross underfunding has become the norm.

Among other matters, United's unions are upset at the company's warning that it is likely to terminate their pension plans and replace them with less-generous retirement programs.

In addition to seeing their pensions cut, workers have also lost healthcare benefits when companies terminate their pension plans.

In the past, companies have successfully fought to keep the additional information secret, saying termination data was irrelevant because they did not plan to terminate their pension plans.

Most companies on the list are in decent financial health and are not likely to terminate their pension plans, even if underfunded.

Mr. Dellinger estimated that steel companies could save as much as $3.30 an hour per employee by declaring bankruptcy and terminating their pension plans.

United has said it may terminate its pension plans as it tries to emerge from Chapter 11 bankruptcy protection.