Less than a year ago, American Airlines unveiled new uniforms for front-line workers, including pilots and flight attendants, that it hoped would demonstrate the carrier was taking a fresh approach following its merger with US Airways.

But for much of the past year, some employees have complained the new uniforms, made by a company called Twin Hill, were causing allergic reactions, and, in some cases, making them ill. American tested the uniforms and found them safe, and Twin Hill also stood by them. But the union representing flight attendants said it had received more than 3,500 reports of “suspected reactions.”

During American’s annual meeting last week, one flight attendant said her colleagues were suffering various ailments, including bronchitis, sinus problems, thyroid issues and racing heart rates. Flight attendants have had more complaints than other work groups.

American gave employees a short-term solution, allowing them to wear look-alike uniforms made by other vendors. But on Wednesday, the airline said it would drop Twin Hill when its contract expires in 2020, telling employees in a memo that it wants to create a “uniform all team members wear with confidence.”

The Association of Professional Flight Attendants endorsed the decision, even though it means some of its members may wear the current uniforms for at least two more years. “We’ll continue to aggressively monitor this issue, as well as any other matters that affect the health and well being of our members,” the union said in a statement.

In a note to employees, American said it will take at least two years to prepare new uniforms. They’ll be based on the current design, but the new supplier will use different materials. Until then, American employees may wear one of three other uniforms that look similar to the Twin Hill ones, but are made by other companies. Or they can continue to wear the Twin Hill uniforms.

The uniform issue has vexed American executives for months. The airline’s leaders tried to quell anxiety earlier last year when some executives started wearing the uniforms to work, but that didn’t help. Executives have also noted that “most” employees have been wearing new uniforms without complaint.

But though American’s testing found nothing that should cause reactions, the issue persisted, and it was a major topic during the question and answer period at the airline’s annual meeting. American CEO Doug Parker said his team was working on a solution but asked for patience.

“There is not a short-term solution to 80,000 uniforms,” he said during the meeting. “We do care about our team. We are working really hard to get to a point where all of our team feels comfortable in the uniforms they have.”

Parker, who took over American in 2013 after merging it with US Airways, where he was CEO, has made improved employee relations a priority. Morale at American was lagging after the carrier’s 2011 bankruptcy, and for a long time, even after the merger, some front-line employees were paid less than workers at other airlines.

American only rectified the pay issue in April when executives decided unilaterally to pay flight attendants and pilots more money, even though their labor contracts were not up for renewal. Some investors did not like the move, but Parker has argued American must reward its employees if it expects them to provide a high level of service to customers.

Still, the uniform concern has been a sore point for some vocal employees. On social media, Heather Poole, a New York-based flight attendant, author and media personality, has been critical of the airline for not withdrawing the uniforms. In a Facebook post on Wednesday, she blasted her employer for waiting to change providers until 2020.

“How many more people will be affected over the next two to three years by the uniform crisis?” she asked. “I won’t celebrate until the uniform is recalled.”

Photo Credit: American Airlines unveiled its new uniforms to great fanfare last year. But it will drop the company that makes them in 2020. American Airlines