American Airlines is seeking communications between Mayor Rahm Emanuel, his top aides and United Airlines in an attempt to determine whether a United threat to pull its corporate headquarters out of Chicago prompted the mayor to award five additional gates to O’Hare Airport’s largest carrier.

United spokesman Charles Hobart countered, “We never threatened to leave Chicago or move the corporate headquarters, nor did we ever discuss it.”

The Freedom of Information request, obtained by the Chicago Sun-Times, clearly states what American suspects may be Emanuel’s motivation for the five-gate deal that American contends tilts the playing field in favor of hometown United.

It asks for copies of emails and other documents in the city’s possession “between May 1, 2016 and Sept. 30, 2016 regarding United’s potential corporate relocation and the possibility of United headquarters leaving Chicago.”

American’s sweeping document request also seeks communications between Oct. 1, 2015, and Dec. 1, 2016, regarding the “construction, allocation or use of gates at O’Hare” as well as communications since Nov. 1, 2017 on gate construction and allocation and “discussions/ negotiations related to a new airline use and lease agreement.”

Mike Minerva, American’s vice president of government and airport affairs, said the internal communications between Emanuel, his top aides and United are critical to determining why Emanuel cut an 11th-hour deal to award five more gates to United.

“We want to know if we’re getting a fair shake here and being allowed to grow,” Minerva said Tuesday.

“The coordinated resistance by the city and United to our request for three gates — to build gates already approved as part of the plan, but build them sooner — feeds our concern that there’s an agreement not to allow us to grow.”

Minerva said the internal communications should “solve the mystery of when and how the five-gate agreement was made.” Was it 2016, as United has claimed? Or was the deal cut in 2018?

More importantly, Minerva said American wants to know “what the quid-pro quo” was.

“What did United give the city for that? What were the understandings and how do those affect American and our future here in the city. . . . We fear that the city has basically chosen United as the airline that it wants to do business with here more than American,” Minerva said.

“We were negotiating this multibillion-dollar lease and it all flipped like a switch. . . . It’s premature for us to say whether we’re gonna sue or not sue because we don’t know what happened.”

Asked specifically about a threat by United to move its corporate headquarters out of Chicago, Minerva said, “We have heard that has been discussed.”

In 2012, United moved its corporate headquarters from Elk Grove Village to Chicago’s Willis Tower, formerly known as Sears Tower.

Aviation Department spokesperson Lauren Huffman agreed that City Hall “never received such a threat” from United.

“Our focus has never been on benefiting any one airline. Our focus is on benefiting the City of Chicago, modernizing O’Hare, fueling our city’s economic engine and creating 60,000 jobs in the process,” Huffman wrote in an email.

American stands alone in opposing Emanuel’s $8.5 million O’Hare expansion plan because of the five additional gates awarded to United.

On Thursday, the City Council’s Aviation Committee will be asked to sign off on the new lease — with or without American — and start the ball rolling by authorizing a $4 billion borrowing retired by newly negotiated airline leases that include higher landing fees, gate and terminal rents.

Deputy Mayor Bob Rivkin has scoffed at American’s threat to file a lawsuit, shrink its dual-hub at O’Hare or both in the high-stakes dispute over new gates.

Rivkin has said American’s only alternative is to continue to use O’Hare as a “non-signatory” airline and that would be “irrational” because, “They would have no control, no input and no assurance of gate space or club space. They couldn’t build out what they want to build out.”

Minerva countered, “This lease agreement harms our business here, and over the long run, it makes it very difficult for us to compete. So, you may see an erosion in our position here as a direct result. And if we see this lease is the future in Chicago, we’ll have to look at all sorts of decisions we make. We are very concerned about the competitive environment in Chicago both because of the terms of the lease and because the administration has so blatantly and obviously sided with our competitor.”