According to the Denver Post, the American Civil Liberties Union (ACLU), the ACLU of Colorado, and the law firm Holwell Shuster & Goldberg filed a sex discrimination complaints against Frontier Airlines on Tuesday on behalf of Denver International Airport-based flight attendants, Jo Roby, who’s from Boise, Idaho, and Stacy Rewitzer of Denver.

The two flight attendants, who both have worked at Frontier for over a decade, claim they were forced to take excessive unpaid leave because Frontier reportedly has a policy that prevents breastfeeding employees from pumping breastmilk while on duty. According to the Denver Post, the airline does not offer a set amount of maternity leave; employees are instead limited to using sick or vacation days, and any unpaid time they have under the Family Medical Leave Act.

In a statement to NBC News, a Frontier Airlines spokesperson said that the airline’s policies and practices adhere to federal and state law.

“Our policies and practices comply with all federal and state laws as well as with the relevant provisions of the collective bargaining agreement between Frontier and its flight attendant group,” the statement said, according to NBC. “We have made good-faith efforts to identity and provide rooms and other secure locations for use by breast-feeding flight attendants during their duty travel.”

The two complaints, which were filed with the Equal Employment Opportunity Commission, come just one year after four Frontier pilots filed similar charges. The complaints, according to the ACLU, seek “clean and convenient” accommodations for on-duty pumping,”including on board during flight when necessary, during training, and at airports.” They also seek short-term alternative ground assignments to better accommodate employees’ breast pumping needs. In addition, the complaints seek “meaningful” parental leave, and “relief from the current strict attendance policy that penalizes flight attendants who miss work due to pregnancy,” according to the ACLU.

In an article detailing her experience, Roby claims that she often worked 10-hour duty days of back-to-back flights, and had no time to pump in between flights. She notes that delaying pumping for more than a few hours can cause pain and infection.

“I am bringing these charges not just for me and my daughter, but also for future flight attendants and their families,” Roby said in a statement, according to the Denver Post. “No one should have to choose between being the mom she wants to be and pursuing the career she loves.”

And while Rewitzer said she “loves her job as a flight attendant for Frontier Airlines,” she said in a statement to the Denver Post that she “shouldn’t have to choose between my job or my health and breastfeeding my child.” She added: “I’m proud to stand with the pilots who stood up to Frontier before us.”