Aloha Airlines is just the latest U.S. carrier to propose shifting its pensions obligations to the federal Pension Benefit Guaranty Corp.

United Airlines, which filed for bankruptcy protection in 2002, earlier this year received court approval to transfer $9 billion in pension obligations to the PBGC.

Like Aloha, United said it needed to shed its pension to emerge from Chapter 11 bankruptcy.

The PBGC is a federal corporation created under the Employee Retirement Income Security Act of 1974 to step in when companies are unable to meet their pension obligations.

The agency receives no money from general tax revenues. Operations are financed largely by insurance premiums paid by companies that sponsor pension plans and by PBGC's investment returns.

It guarantees payment of basic pension benefits for about 44 million U.S. workers and retirees participating in more than 31,000 private-sector defined benefit pension plans.

When the government takes over an airline's pension plan, highly compensated employees such as pilots and executives could see a dramatic drop in benefits.

That's because federal law limits annual pension payments for plans canceled in 2005 to $45,613 for people who retire at age 65.

The PBGC itself is in financial trouble as a result of taking on large obligations, such as the United Airlines pension.

The PBGC lists a deficit of $23.3 billion and some fear that it will require a taxpayer bailout to remain solvent.