The logos for Time Warner and AT&T appear in June above trading posts at the New York Stock Exchange. (Richard Drew/AP)

The Justice Department on Thursday filed an appeal challenging its loss in the AT&T-Time Warner antitrust trial, according to court documents, a potential warning for the deals that are expected in the wake of the $85 billion acquisition.

AT&T completed its acquisition of Time Warner a few weeks ago after a federal judge rejected the Justice Department’s argument that the deal would be anti-competitive.

The case was closely watched as an indicator of how courts would treat mergers of companies in different industries. AT&T is one of the country’s biggest telecommunications providers, and its purchase of Time Warner allowed it to pick up some of the biggest media brands in the United States, including HBO and CNN.

During the trial, the Justice Department said the merger could raise prices for consumers and for the companies' rivals, to the tune of hundreds of millions of dollars a year. In response, AT&T said the deal would actually lead to lower prices for TV viewers.

Soon after the deal closed, AT&T announced a price increase for DirecTV Now, the company’s online streaming video service. The company said it was increasing rates to bring the product in line with the rest of the market. But it is unclear how that price hike could affect the litigation. Some analysts said it could reflect negatively on judge Richard Leon’s analysis of the case and possibly benefit the Justice Department. The agency did not respond when asked whether the price changes contributed to its decision to appeal.

“My guess is that the government is going to try to show that a lot of important evidence was rejected by the judge, and the judge put too much weight on the testimony of the merging parties,” said Gene Kimmelman, a former Justice Department antitrust official who now leads Public Knowledge, a consumer advocacy group that opposed the merger.

The appeal could be seen as a warning sign for companies that have pursued their own mergers in the wake of Leon’s decision, Kimmelman added.

AT&T said in a statement Thursday that Leon, a judge in the U.S. District Court for the District of Columbia, correctly decided the case.

“While the losing party in litigation always has the right to appeal if it wishes, we are surprised that the DOJ has chosen to do so under these circumstances,” said David McAtee, AT&T’s general counsel. We are ready to defend the court’s decision at the D.C. Circuit Court of Appeals.”

AT&T’s stock fell by more than 1.4 percent in after-hours trading.

No matter how the Justice Department’s appeal unfolds, AT&T’s completed acquisition of Time Warner could prove difficult to untangle. For now, little is expected to change. Although Time Warner — now renamed WarnerMedia — operates independently from AT&T’s telecommunications business, integrating the companies under one banner still requires detailed coordination, said Jeffrey Blumenfeld, an antitrust lawyer at the firm Lowenstein Sandler in Washington.

The day after Leon delivered his ruling, Comcast made a $65 billion offer for 21st Century Fox, in an attempt to outbid Disney for Fox’s entertainment assets. The offer is now at $71.3 billion as Disney outbid Comcast for Fox. Antitrust experts are watching that potential merger closely as another example of the media consolidation that’s swept the industry. In recent years, Verizon purchased AOL and then Yahoo in an effort to create an online advertising business.

The last time the Justice Department challenged a completed deal was in 2017, when the agency sued to undo a merger in the aviation fuel filtration industry. The two sides settled later that year after the company defending the suit agreed to spin off parts of its business.

Even if the government loses its bid for an appeal, it could still sue AT&T in the future if it observes evidence of anticompetitive behavior, Blumenfeld said.

“If a year or two from now, it turns out the merger is anticompetitive, the DOJ could try it again,” he said.

At the core of the Justice Department’s case was the assertion that AT&T could use its newfound Time Warner content as a way to harm rival TV services — both traditional cable companies as well as new, streaming video services such as Hulu. The government’s theory was that AT&T would raise the price of licensing Time Warner’s content so that other TV services would have to pay more, passing along those extra fees to consumers. That arrangement could also indirectly benefit AT&T over the long term, the Justice Department said, because customers fed up with the extra fees would have more reason to switch to AT&T.

AT&T argued in district court that the merger is necessary to help it compete against tech companies such as Netflix and Google. By marrying AT&T’s telecom network with Time Warner’s content, executives said, the merger would create a new, data-driven advertising business. Customer data has propelled Netflix and YouTube to the forefront of the media and entertainment industries, showing executives precisely what consumers like to watch and when. The results have paid off, particularly for Netflix: The company this week earned 112 Emmy Award nominations, more than HBO. HBO has sat atop the Emmy nominees' list for the past 17 years.