WASHINGTON -- Wall Street, young workers, a couple of airlines and taxpayers could come out as winners in the pension changes made by Congress.

Some older employees, as well as truck drivers and construction workers hoping to retire early, might not fare as well.

The legislation passed by the Senate late Thursday and sent to the president could accelerate corporate America's shift away from traditional pensions, experts said yesterday.

The bill, expected to get President Bush's signature, tightens funding requirements for companies that are behind on their contributions to traditional, defined-benefit pension plans. Now they'll have to make up the shortfall within seven years. Those with "at-risk" plans will have to accelerate their contributions.

That bill could make companies even more eager to move to defined-contribution plans such as 401(k)s.

The new funding rules "will inject a lot of unpredictability, and therefore I think accelerate the move away from defined-benefit plans," said James Klein, president of the American Benefits Council, which represents companies with traditional defined-benefit plans.

Businesses have already been shifting away from traditional pensions. The number of such plans peaked at about 115,000 in 1985, but had dropped to about 29,000 in 2004. Companies have increasingly looked to get away from promising retirement benefits today that they will have to pay decades from now.

Instead, they've shifted to plans such as 401(k)s where employees put in their own money, often with a match from the employer. In plans like that, once the company pays its match, its obligation is finished.

The new pension law could increase the difference between the certainty of a limited 401(k) match and the uncertainty of a pension obligation due decades down the road.

Here's how some of the major players in the legislation may be affected:

EMPLOYERS

The defined-benefit plans run by employers are now underfunded by $450 billion, and the bill requires plans to reach full funding levels in seven years. Seriously underfunded "at-risk" companies must contribute at an accelerated rate.

Frank McArdle, manager of the Washington office of Hewitt Associates, a human resources consulting firm, didn't think the funding rules would of themselves contribute to more ditched plans. "We think in the end companies will figure out a way to work with them."

The Congressional Budget Office concluded that companies will actually contribute less to their plans over the next few years as the new funding rules are phased in, but will start making higher contributions in about five years.

Two companies pleased about the legislation are Delta Air Lines and Northwest Airlines Corp., which have filed for bankruptcy and have frozen their defined benefit pension plans. Delta intends to terminate its pilots' pension plan. Concerned that the two airlines would dump their plans, underfunded by a total of more than $10 billion, on the government, lawmakers gave them an extra 10 years beyond the seven years that other companies get to catch up.

Not quite as pleased were American Airlines and Continental Airlines Inc., the only major airlines with active defined-benefit plans. Unless they freeze their plans, entitling them to the full 10-year extension, they will get three years on top of the seven-year payback time.

WORKERS

The bill, while stabilizing a shaky system, does not ensure there will be a defined-benefit plan in a worker's retirement future. Half the workers in private industry have no pensions, and the legislation "doesn't do anything for that," said Karen Friedman, policy director of the Pension Rights Center.

A Hewitt Associates survey of 227 employers last year found 29 percent were very or somewhat likely to close participation in defined-benefit plans during the year.

The AARP said workers get shortchanged in a provision that adds legal certainty to cash balance plans, "hybrids" currently in legal limbo because of a lawsuit against IBM filed by employees claiming age discrimination. The bill, said the AARP's David Sloane, "may lead to discriminatory plan designs that stop or reduce benefits for older workers."

Experts agree that young workers in particular will be big winners from provisions promoting automatic enrollment into 401(k) programs. Research by the Investment Company Institute and the Employee Benefit Research Institute found that 401(k) participation rates among low-income workers would more than double, from 42 percent to 91 percent, under automatic-enrollment plans.

The bill also encourages savings by making permanent a 2001 law allowing for increased annual-contribution limits to individual retirement accounts, or IRAs. This would mainly benefit higher-income households.

All this will be a boon to Wall Street firms, which will see a rise in investors.

TAXPAYERS

The Pension Benefit Guaranty Corp., the federal agency that insures pension plans, has racked up deficits of $22.8 billion, mainly from taking over defunct steel and airline plans. The PBGC now operates on premiums and interest earnings, but the concern is that a rash of terminations could result in a massive taxpayer bailout.

But most experts discount comparisons to the bailout for the savings and loan industry in the 1980s, noting that PBGC liabilities can be stretched out over 30 or 40 years.

If the legislation just keeps the airline pensions afloat, the PBGC, and the taxpayer, come out winners.