ATLANTA – In the protracted fight over creating metro Atlanta's second commercial airport in Paulding County, supporters of the idea have long alleged that Delta Air Lines is funding lawsuits filed by residents challenging that effort.

Delta said it's no secret that it opposes the commercialization of the Paulding airport, 38 miles northwest of downtown Atlanta, because it wants to protect its hub at Hartsfield-Jackson International Airport.

But the Atlanta-based airline has never publicly admitted to giving financial aid to residents who file lawsuits or to the grass-roots efforts. Last week, Delta filed a friend-of-the-court brief weighing in on a legal effort to force an anti-commercialization group to reveal its funding source.

The commercialization of the Paulding airport has been put on hold amid multiple lawsuits. Supporters of the effort said Delta's opposition raises questions about who is behind "grass-roots" groups, if the votes of local officials are being influenced, and what right people have to know if large corporations are funding certain groups.

Delta in its brief said the anti-commercialization group, called "the Committee to Protect Paulding County," has "a First Amendment right to engage in political activity free from unnecessary government interference, including compelled public disclosure in civil litigation."

But Propeller Investments, which runs the company that Paulding's airport partnered with for commercialization, said in a written statement: "Not only is Delta trying to stop commercial air service, job creation and economic development in Paulding County, they are also desperately trying to make sure that the extent of their efforts are not made public."

When asked late last year how much Delta has spent on anti-commercialization efforts in Paulding, Delta CEO Ed Bastian told the Atlanta Journal-Constitution that "any legal costs to represent ourselves" have been "minimal."

The Atlanta Journal-Constitution in 2014 reported that "the Committee to Protect Paulding County" was formed by Stefan Passantino, then an attorney at law firm McKenna Long & Aldridge, as a nonprofit 501(c)(4). That's a classification that includes issue advocacy groups that are allowed to collect money without having to disclose who gave it to them.

McKenna Long & Aldridge has represented Delta in legal matters. Passantino said at the time that Delta "is not the client here." President Donald Trump appointed Passantino last year as his deputy White House counsel for ethics and compliance.

Listed as CEO of "the Committee to Protect Paulding County" is Chip Lake, a Republican consultant and former adviser to U.S. Rep. Phil Gingrey.

Silver Comet Terminal Partners, the company run by Propeller Investments that the airport partnered with for commercialization, sought to compel depositions of Lake and his committee to find out whether Delta donated to the committee.

A Paulding County Superior Court judge ruled that Lake and "the Committee to Protect Paulding County" must testify. They filed an appeal, and Delta filed a brief in support of Lake and the committee in state appellate court.

According to filings in the case, Lake on a public podcast said he was working for "a major airliner in Atlanta" that is "fighting an airport expansion for a regional airport on the western side of the state." Later, he wrote that he "misspoke on the podcast" and "was not under oath."

Delta in its filing cited the 2010 Citizens United ruling that expanded free speech rights of corporations through campaign donations.