Southwest Airlines offered its flight attendants voluntary leave with partial pay Wednesday in a move to trim its workforce and payroll, even as the U.S. Senate approved a stimulus package with $50 billion in aid for the struggling airline industry.

Now, two unions at Dallas-based Southwest say the airline may be preparing to reject any federal stimulus because of the strings attached to it, including restrictions on dividends and share buybacks, requirements to keep employment levels stable through September and limits on executive pay.

Treasury Secretary Steve Mnuchin may also require the airlines to give an equity stake in exchange for grants, the Wall Street Journal reported Thursday.

“Some Airlines may want to try and weather the storm while laying off members to get them off the payroll,” said Bret Oestreich, national director of the Aircraft Mechanics Fraternal Association, which represents about 2,800 employees at Southwest.

Airlines Parked jets and fewer flights: Government aid paves way for airlines to shrink during COVID-19 crisis In the coming weeks, more and more planes will be parked on airport taxiways as airlines shrink to respond to decimated demand and timid passengers. By early April, airlines will likely be flying a fraction of the planes they did at this time a month ago, both because passengers are abandoning flights and because the bailout packages lawmakers are set to approve gives lets them pay workers to sit at home. By

Southwest is offering flight attendants voluntary paid time off for May and June at “50% of the minimum line value." The deal would also preserve benefits, although flight attendants would still need to complete paid training requirements.

Transport Workers Union Local 556, which represents Southwest’s 16,000 flight attendants, is telling members not to take the deal, especially because it comes just before final congressional approval of the stimulus package that could guarantee them full pay in the coming months.

“The company created this emergency time off program blindly, quickly, and with complete disregard for what is being negotiated and approved by Congress,” TWU Local 556 said in a letter to members. "Southwest Airlines also claims that they ‘retain the right to reject the government funding and the strings that come with it.’”

Southwest CEO Gary Kelly spent weeks in Washington lobbying lawmakers and federal leaders on the stimulus package, but the airline has been quiet about the bill since the weekend, when senators closed in on a deal. In the version of the bill passed Wednesday night in the Senate, airlines would get $25 billion in loans and $25 billion in grants for “the continuation of payment of employee wages, salaries, and benefits.”

The airline is in desperate need of some kind of help, Kelly has said in messages to employees.

“The CARES Act is massive, includes many complexities and nuances, and provides the Departments of Treasury and Transportation with the authority to interpret and implement the bill’s many provisions and conditions,” said a statement from Southwest Airlines spokesman Chris Mainz. “We also understand the Treasury Department will have several days to outline the procedures for applying for government assistance, after the bill is signed into law.”

Southwest may be in better financial shape than many of its competitors, but it still has struggled to keep up with the swiftness and depth of the sudden drop in airline traffic. TSA data shows that U.S. passenger traffic has dropped almost 90% compared to a year ago. Last week, a Southwest executive said planes were flying less than 20% full.

Several crew members have reported they are flying planes with as few as three to eight passengers.

Southwest is sitting on $6.2 billion in cash to help it through the coming months. Its employee salaries and benefits last year totaled $8.3 billion.