While most U.S. corporations contribute cash to their pension plans, others make the choice to contribute common stock or new debt to their plans.
Boeing Co., Chicago, contributed $3 billion in its own common stock to its primary U.S. pension plan in November.
Spokesman Bryan Watt, who in February confirmed the contribution, did not reply to requests for further information.
While corporations traditionally contribute cash for their pension plans, it is not unheard of to contribute a company's own common stock.
Doing so can help a company that might not want to devote cash to contributions, said Ned McGuire, Los Angeles-based managing director and member of Wilshire Associates' investment management and research group, in an interview.
"One of the complications is your stock is typically tied to how your company is doing," Mr. McGuire said, "and that's also potentially tied to how the rest of the economy is doing."
"The other risk is how do you get out of that common stock?" he said. "Companies have more information about their common stock than a typical institutional investor. Liquidating that investment may require additional oversight."