Lawyers for the American Civil Liberties Union on Tuesday broadened its legal battle on behalf of pregnant and breast-feeding mothers by filing another discrimination complaint against Frontier Airlines.

It is the second time the ACLU and its pro bono partner, New York litigation boutique Holwell Shuster & Goldberg, has gone after Frontier. A prior complaint on behalf of four women pilots is pending before the U.S. Equal Employment Opportunity Commission.

Jim Faulkner, head of corporate communications at Frontier, said in a statement, “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. 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.”