“The time period for the US Department of Justice to complete its regulatory investigation of the proposed combination of Alaska Airlines and Hawaiian Airlines under the HSR Act has expired,” the airline said in a statement on its website.

“This is a significant milestone in the process to join our airlines,” the company said, adding that it is now awaiting next steps with the US Department of Transportation (DOT).

Alaska Airlines, which had announced the merger last year, agreed last week to extend the review period of its proposed acquisition of Hawaiian Holdings with the DOJ.

“Today, the proposed merger of Alaska Airlines and Hawaiian Airlines cleared an important milestone. The regulatory review period for the US Department of Justice has ended,” Hawaii’s governor Josh Green said.

“The merger will vastly expand the number of destinations throughout North America for Hawaii residents that can be reached nonstop or one-stop from the islands, and HawaiianMiles members will retain the value of their miles while gaining access to more destinations around the world.”

Mergers and acquisitions in the aviation industry have faced tough scrutiny from regulators. Earlier this year, a federal judge blocked JetBlue Airways’ planned US$3.8 billion acquisition of ultra-low-cost carrier Spirit Airlines.