After a nearly yearlong courtship, the union became official Thursday: American Airlines and US Airways have formally announced plans to merge.

An early morning announcement by the airlines confirmed reports widely circulated after boards of both companies approved the merger late Wednesday.

The move brings stability to one of Miami-Dade County’s largest private employers more than a year after the airline and its parent company filed for bankruptcy protection, leaving the fate of thousands of employees — and the largest carrier at Miami International Airport — in question.

According to the Thursday announcement, the deal was approved unanimously by the boards of both companies, creating the world’s biggest airline with implied market value of nearly $11 billion, based on the Wednesday closing price of US Airways stock. The airline will have close to 100,000 employees, 1,500 aircraft, $38.7 billion in combined revenue.

The deal must be approved by American’s bankruptcy judge and antitrust regulators, but no major hurdles are expected. The process is expected to take about six months, according to a letter sent to employees Thursday by American CEO Tom Horton.

Travelers won’t notice immediate changes. The new airline will be called American Airlines. It likely will be months before the frequent-flier programs are merged, and possibly years before the two airlines are fully combined. The new airline will be a member of the oneWorld airlines frequent flier alliance.

And for Miami travelers, it’s unlikely that much will change at any point. American and regional carrier American Eagle handled 68 percent of traffic at the airport last year, while US Airways accounted for just 2 percent. American boasts 328 flights to 114 destinations from Miami.

“We don’t expect any substantial changes at MIA if the merger occurs because our traffic is largely driven by the strength of the Miami market and not the airlines serving it,” said airport spokesman Greg Chin.

American has said for more than a year that its long-term plan calls for increasing departures at key hubs, including Miami, by 20 percent. That pledge has already started to materialize; in recent months, the airline has added new service to Asuncion, Paraguay and Roatán, Honduras.

During its bankruptcy restructuring, about 400 American employees lost jobs, leaving American and its regional carrier, American Eagle, with 9,894 employees in Miami-Dade County and 43 in Fort Lauderdale. US Airways has few employees in the area.

“It really isn’t going to affect Miami in a very major way anytime soon,” said Michael Boyd, an aviation consultant in Evergreen, Colo. “Only because US Airways isn’t a big player in South Florida.”

At Fort Lauderdale-Hollywood International Airport, American and US Airways combined would still only be the fifth-largest airline after Southwest, Spirit, JetBlue and Delta, a spokesman said. The two airlines have little overlap in routes from Fort Lauderdale.

Despite the lack of major changes, Boyd said the merger would be a good development for Miami.

“It should be positive for the employees and it should be positive for the communities that the airlines serve,” he said.

Robert Herbst, an independent airline analyst and consultant, said US Airways will add a “significant amount” of destinations in the Northeast, including Philadelphia and Washington, D.C.