Hundreds of employees are complaining that the current uniforms are causing health problems.

More than 500 flight attendants have filed a federal lawsuit against Lands’ End, the company that makes the uniforms. They say they’ve experienced a variety of health problems since Delta introduced the uniforms back in May 2018 such as skin blisters and rashes, breathing difficulties, migraines and more. However, Delta is saying that tests show that the uniforms are safe.

The flight attendants claim to have conducted their own tests and found that the material in the uniforms were made using chemicals and heavy metals that surpass the industry safety standards.

As a result, Delta is starting the process to change the uniforms. In the meantime, flight attendants have been given permission to wear other, similar-looking clothing.

The airline revealed that the change will cost millions of dollars, but the new permanent uniforms should be in place “hopefully in late 2021,” an email sent out by the company stated. New clothing will be available in the meantime starting in May.

The lawsuit is not the only thing Delta is dealing with right now. The airline is also facing a union organizing campaign by the Association of Flight Attendants, which is seeking to represent 25,000 flight attendants at the company.