Some of the restrictions set out by the legislation, like a temporary halt on companies using their own money to buy back stock, appear to apply to all company loans. But a commitment by companies to maintain hiring at or close to recent levels is not required across the board. It would apply to the aid for airlines and companies deemed important to national security, but only through the end of September. On Friday, United management told staff that the federal aid would prevent any substantial reductions in staff or pay through September, but suggested that layoffs may come if the recovery was as slow as the company expected.

Treasury could also demand stock in exchange for supporting airlines and companies like Boeing.

For some executives, giving the government shares in their company could be a big sticking point. In a TV interview last week, Mr. Calhoun, the Boeing chief executive, suggested he would not be interested in a rescue package that gave the federal government stock in the company.

“I don’t have a need for an equity stake,” he told Fox Business. “If they force it, we just look at all the other options, and we’ve got plenty of them.”

While the government has laid out initial guidance on terms for the $17 billion available to companies deemed essential to national security, it is expected to release more specific terms in the coming days. Until those terms are clear, Boeing is holding off on making a decision, two people briefed on the company’s deliberations said.

The airlines have not set out a clear position on giving the taxpayer stock.

On Thursday, the chief executive of Southwest Airlines, Gary Kelly, told employees that the airline planned to apply for the grants to pay workers, but a spokesman declined to say whether the airline would be willing to give the government an equity stake in exchange for the assistance. Last week, Mr. Kelly said that the legislation only “gives us another option” and that the company could also “raise capital in the private markets.”

American, which has said it would seek aid from the government, referred questions about whether the government should take a stake in airlines to Airlines for America, an industry group. The group and United Airlines declined to comment. Delta Air Lines did not respond to a request for comment.

But on Wednesday, the unions that represent flight attendants at several major airlines urged Mr. Mnuchin not to exercise his power to take stock in the airlines. They argued that if he did so, he could scare off executives from accepting the aid, which would, in turn, mean more layoffs.