Updated

Fans at this weekend’s Chicago Cubs games shouldn’t be surprised to see a picket line out in front of Wrigley Field — but it’s not the park’s employees who are up in arms.

The Chicago Business Journal reports that two labor unions representing American Airlines mechanics are planning to protest outside the stadium over fears that their jobs will be outsourced to South America and China. According to the Dallas News, the Transit Workers Union had also been negotiating for a new contract with the carrier since 2015, following American’s merger with U.S. Airways.

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As for why they’re picketing at Wrigley Field? American Airlines was chosen as the official airline of the Chicago Cubs and Wrigley Field in 2015, and American serves as the Cubs' only airline sponsor.

American Airlines, meanwhile, claims the company has recently offered the TWU a new contract, but the workers have yet to respond.

In a statement obtained by Fox News, a spokesperson for the airline said “American is proud to employ more maintenance and fleet service team members, and do more maintenance and fleet service work in-house, than any other U.S. airline. That’s the case today and will remain the case under the proposal we have presented to the TWU-IAM Association.

"We’re incredibly thankful for our skilled and well-trained team and want to get them an industry-leading contract as soon as possible. We look forward to the Association’s response to our comprehensive proposal we offered last month.”

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The backlash over American Airlines’ business plans can be traced back as far as March, shortly after workers at the airline’s maintenance plants in the United States learned of the company’s plans to build a multi-million dollar maintenance facility in Brazil. In response to this, as well as the contract dispute, AA workers organized a picket line at the Dallas Fort Worth National Airport in July, attracting more than a thousand picketers, according to Dallas News.

But in March, the airline also claimed that the opening of its Brazil facility “will not impact work already done in Tulsa and the U.S.,” and that the hangar will be used for only light repairs and mantenance, rather than complete rebuilds, reported News On 6.

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The groups also saw an increase in pay as far back as August 2016, but a union leader told CBS Dallas he's not just worried about money.

“It’s not about the pay. It’s about everything that goes around the pay,” Greg Cosey, the vice president of Local 513, told CBS Dallas shortly before the July protest. “It’s about benefits. It’s about the future of our members, really.”