Sen. Tammy Duckworth (D-IL) on Wednesday urged the Trump administration to expand bonuses awarded during the recent government shutdown to qualifying Federal Aviation Administration workers to more employees at the agency. 

Transportation Secretary Sean Duffy announced last month that air traffic controllers and technicians who had a perfect work attendance record during the shutdown would receive a $10,000 bonus, citing his “heartfelt appreciation for [employees] going above and beyond in service to the nation.”

In a letter to Duffy this week, Duckworth demanded that the bonus be given to all controllers and technicians, regardless of their attendance record. She said that “excluding 96 percent” of the FAA’s controller and technician workforce from the bonus was “unfair, divisive, and disrespectful,” in the letter first obtained by CBS News.

The majority of FAA staffers called out at some point amid Washington’s gridlock, as federal employees worked without pay during the longest shutdown in U.S. history.

Only 776 out of around 20,000 FAA employees qualified for Duffy’s bonus, as they showed up for work without fail despite the suspended pay. 

Duffy has stressed that all FAA workers, including those who called out, received full back pay after the shutdown concluded in early November. But he has argued that those who held a perfect attendance record warranted an additional reward. 

“I think in the future, a lot of controllers would think, ‘Hey, there could be a reward when I show up, and I’m going to do all I can to be there every single day to serve the American people. And I know that I’ll get paid at one point, but if I have a perfect attendance record, there could be a reward at the end of that rainbow,’” Duffy told reporters last week. 

However, in her letter to the secretary, Duckworth expressed concern that the bonus plan could “create a perverse and dangerous incentive that threatens to weaken NAS safety during future shutdowns.”

“Controllers will have a financial incentive to avoid using authorized leave—even while suffering from illness that degrade controller performance and risk infecting an entire cadre of employees working a shift,” Duckworth wrote. “Air Traffic Organization jobs are extremely stressful for good reason: one mistake may be deadly. These dedicated professionals must be at their best when on the job, but your policy encourages Air Traffic Controllers and Technicians to show up regardless of their health. That is incredibly dangerous. Sick leave exists for a reason.”