The United States Department of Transportation (DOT) has cleared a review by the Justice Department (DOJ) of the proposed USD1.9 billion merger between Alaska Airlines and Hawaiian Airlines and says it is now itself "reviewing the application and can only approve a transfer if it is in the public interest."

The DOJ did not make an immediate announcement, but Hawaii's state governor Josh Green issued a statement in which he hailed the end of the official review period as "an important milestone". Alaska Airlines equally marked the "significant milestone" in a statement on its website.

"During the DOJ’s review, Alaska worked closely with the Hawaii Attorney General to reinforce and expand upon our commitments for the future of Hawaiian Airlines and to Hawaii consumers. These include plans to maintain the Hawaiian Airlines brand and local jobs and continue providing strong service between, to, and from the islands," it said.

The DOJ thrice extended its review period, initially scheduled to end on August 5, then postponed it to August 15, then to August 16, and finally until August 20.

The proposed merger is now subject to the DOT’s approval of an interim exemption application that Alaskan and Hawaiian have previously jointly submitted, and "following that step, we will complete work to close the transaction and proceed with integrating the two companies," Alaska Airlines said.

A US court recently blocked a consumer lawsuit to stop the deal.

The parent companies of both airlines, Alaska Air Group and Hawaiian Holdings, announced their agreement to merge on December 2 last year. As part of the deal, Alaska Airlines will assume USD900 million of Hawaiian's debt. The carriers plan to continue operating under their existing brands while integrating their operational systems.