SEATTLE — Alaska Air Group said Sunday it agreed to buy Hawaiian Airlines in a $1.9 billion deal including debt.

The combined company would keep both airlines’ brands, which call the 49th and 50th states their homes. Alaska will pay $18 in cash for each share of Hawaiian, whose stock closed Friday at $4.86. The deal also includes $900 million in Hawaiian debt, which the airlines said brings the acquisition’s total value to $1.9 billion.

The deal still needs approval from the boards of both companies, as well as from the shareholders of Hawaiian Holdings. It will also need the blessing of U.S. regulators, which have shown resistance to more consolidation within the airline industry out of fear it could lead to higher fares.

The companies expect the deal to close in 12 to 18 months.