United Airlines is facing scrutiny from some U.S. lawmakers after accepting federal aid in the last two rounds of stimulus but considering outsourcing catering jobs at five airports.

The group of almost two dozen Congressmen and women want airlines to commit to keeping jobs and avoid outsourcing employment if they want a third round of federal payroll aid, according to Reuters News Agency .

The members of Congress made the request to Treasury Secretary Janet Yellen, according to letters released by Unite Here, the union representing more than 2,500 workers whose jobs are at risk under United's proposal.

"We respectfully request that any new PSP payments to United Airlines and other carriers make clear that any outsourcing of jobs while receiving PSP payments would violate the terms of the program," seven senators wrote in a May 4 letter to Yellen, who has authority over the terms of the aid.

United has apparently solicited bids at five U.S. airports to outsource catering workers.

"Given the unprecedented impact of COVID-19 on our business, United continues to explore ways to do things differently and become more efficient wherever we can," United spokeswoman Leigh Schramm said, adding that the outsourcing proposal is "part of that effort” but that no decisions have been made yet.

United has received $7.7 billion in two previous coronavirus pandemic stimulus packages, designated what is known as the payroll support program (PSP) to keep employees staffed and paid.

Reuters reported that United stands to receive another $2.8 billion under a third package set to run through Sept. 30.