The combined company would maintain both airlines’ brands, an unusual move in an industry where waves of acquisitions have led to four big brands dominating the U.S. market. On Sunday, the companies said Alaska would pay $18 in cash for each share of Hawaiian, whose stock closed Friday at $4.86 after losing just more than half its value in the year so far.

Officials from both companies called the deal a chance to combine two carriers with few overlapping routes, which they said would create a stronger company to compete with the nation’s big four airlines: American, Delta, Southwest and United. It would also create a “clear leader” in the lucrative, $8-billion Hawaiian market, Alaska Chief Executive Ben Minicucci said in a conference call with investors.

“We combine two companies with shared values that have competed and survived longer than most through many industry cycles, enhancing our differentiated business model and creating a stronger competitor to network carriers,” he said.

The deal includes $900 million in Hawaiian debt, bringing the acquisition’s total value to $1.9 billion. The combined airline would be based in Seattle, with Alaska’s Minicucci at its head. The companies forecast that the acquisition would increase profits within two years of the deal closing, which is expected to happen 12 to 18 months from now.

The combined airline would participate in the Oneworld Alliance, which includes American Airlines, British Airways and Cathay Pacific.

Alaska and Hawaiian are both smaller than the nation’s dominant carriers. They said the deal would join two complementary networks, increasing connectivity to 138 destinations for passengers traveling through the continental U.S. and across the Pacific, including nonstop service to 29 international destinations in the Americas, Asia, Australia and the South Pacific.

Hawaiian Airlines has a deep and long history within the islands, stretching back to its incorporation in 1929 under the name Inter-Island Airways.

The companies said that they would keep Honolulu as a key hub and that they were “committed to maintaining and growing union-represented workforce” in Hawaii. Minicucci told reporters at a news conference Sunday that it was “too soon to tell” how many non-union positions would be eliminated once the merger was completed.

“I’m hopeful that the number is not large,” he said of the potential layoffs.

The companies also said the combination would triple the destinations that could be reached within one stop in North America for travelers from Hawaii.

For example, customers cannot currently fly to Washington, D.C., on Hawaiian, but they would be able to through the combined company.

On a call with investors, Hawaiian Airlines Chief Executive Peter Ingram said Alaska had approached his company about a deal and that “the Hawaiian brand will remain an important part of our home state.”

The deal has been approved by the boards of both companies, but it still needs an OK from the shareholders of Hawaiian Holdings. It will also need the blessing of U.S. regulators, who have resisted more airline consolidation out of fear it could lead to higher fares.

The Biden administration is already trying to block JetBlue’s proposed $3.8-billion acquisition of Spirit Airlines, which would subsume the nation’s biggest budget carrier. The Justice Department also won a lawsuit that killed a partnership between JetBlue and American.

The average domestic fare out of Seattle during the spring was $409.93. That was up from $293.08 two years earlier, according to data from the U.S. Department of Transportation. The average domestic fare out of Honolulu during the spring was $367.94, up from $329.93 two years earlier.

But given how little Alaska and Hawaiian’s routes overlap, their proposal may not create much angst in Washington, said Henry Harteveldt, a travel industry analyst at Atmosphere Research Group.

Just as important, he said, neither Alaska nor Hawaiian was an ultra-low fare airline like Spirit. That means combining them would not eliminate the kind of downward pressure on fares that a Spirit buyout might.

The airlines will need to work with their unions as they try to streamline operations, and corporate officials said they have spoken with collective bargaining leaders already. The Air Line Pilots Assn. said Sunday that it was evaluating the proposal and awaiting more details.

Both airlines have historically paid more attention to their employees than competitors, among other similarities in their corporate cultures, Harteveldt said — another reason a merger could work.