Ground workers at American are represented by the Transport Workers Union, while those at US Airways are represented by the International Association of Machinists and Aerospace Workers.
Over the weekend the unions disclosed that they reached an agreement on merger-related seniority. That's a big issue in airline mergers because seniority affects pay and work assignments and, sometimes, who gets laid off after airlines combine workforces. The two airlines also agreed to the deal.
However a seniority agreement alone wouldn't necessarily avoid a fight between the IAM the TWU, both of which belong to the AFL-CIO. Both are likely to want to represent all ground workers at the combined airline, which will keep the American Airlines name and become the world's biggest carrier.
In a letter to TWU President James C. Little and IAM president Thomas Buffenbarger, Trumka said he feared that the two unions would wind up in "lengthy, contentious and bitter campaigns" to keep representing workers that each has held for decades.
"Both of you know that if aggressive representation campaigns are launched, they will inevitably harm both unions," Trumka told the presidents. "As important, it will also be taken for what it is: a portrait of AFL unions at war with one another at a time when we desperately need to focus organizing efforts on the unorganized."
Trumka asked the unions to share representation rights, with each keeping its pre-merger membership.
Separately TWU faces a threat from the Teamsters and the Aircraft Mechanics Fraternal Association to represent American Airlines ground workers.
American, owned by AMR Corp., and US Airways have reached separate seniority agreements with unions for pilots and flight attendants.
AMR filed for bankruptcy protection in 2011 and announced in February that it will merge with US Airway Group Inc. Executives for the airlines expect the deal to win approval from antitrust regulators and to close before the end of September.