Lani Perlman of Holwell Shuster & Goldberg.

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.”

Galen Sherwin, staff attorney with the ACLU in New York, said the group has litigated and successfully settled numerous cases involving pregnant or nursing employees, and has several charges pending now with the EEOC in various parts of the country. Another breast-feeding case against the city of Tuscaloosa, Alabama, is pending before the U.S. Court of Appeals for the Eleventh Circuit, Sherwin said.

The ACLU led the amicus brief effort on the 2015 U.S. Supreme Court case, filed against UPS, that established that failure to accommodate pregnant workers can amount to sex discrimination under federal law.

In Tuesday's complaints to the EEOC, flight attendants Jo Roby, a 13-year Frontier employee, and Stacy Rewitzer, an 11-year employee, said they were forced to take unpaid leave after having their babies. They also said Frontier refused to provide accommodations for them to pump breast milk, and that they were told not to pump while on duty.

The attendants said in their affidavits that they often work 10-hour or longer shifts, but need to pump their milk about every four hours. Their charges assert that Frontier's policies violate federal and state laws against discrimination based on sex, pregnancy, childbirth and disability in employment, including Title VII of the Civil Rights Act of 1964.

Last year the ACLU and the law firm filed similar discrimination charges against Frontier with the EEOC on behalf of the pilots. That claim says the company forces pregnant pilots to take eight to 10 weeks of unpaid leave before their due date; allows a maximum of 120 days of maternity leave, all of it unpaid, and fails to make accommodations to enable pilots who are breast-feeding after they return to work.

Lani Perlman, associate at Holwell Shuster, said, “We did reach out to Frontier before filing the flight attendant charges. We are always pleased to have companies change their policies without litigation, but Frontier did not do so.”

Perlman added, “This is an issue that has come to light throughout the aviation industry after the pilot charges were filed. Some other airlines are trying to address the issue.”

A Milwaukee law firm employment blog reported that last year Delta Air Lines settled a claim by a flight attendant who said Delta violated a New York City human rights law by failing to provide her with space to pump breast milk.

Delta reportedly paid $30,000 and agreed to revise its accommodation policies. An airline spokesperson couldn't address the settlement, but told the blog the company strives “to provide a great place to work … including offering lactation rooms and other reasonable accommodation to new mothers and expectant mothers.”