The merger between Alaska Airlines and Hawaiian Airlines has been approved by the Justice Department, but still needs to be reviewed by the Department of Transportation.

• The deal between Alaska Airlines and Hawaiian Airlines requires approval from the Transportation Department.
• The Justice Department's investigation into the deal ended Tuesday without any legal action to prevent it.

The U.S. Justice Department has cleared the plan of the two carriers to acquire each other after eight months of investigation without any lawsuit to block the deal.

Before the deal closes, the two airlines must obtain approval from the U.S. Transportation Department, but the duration of the process is uncertain.

Since the merger of Alaska and Virgin America eight years ago, the latest combination of U.S. carriers is the largest.

"The deadline for the U.S. Department of Justice to complete its antitrust investigation of the merger between Alaska Airlines and Hawaiian Airlines under the [Hart-Scott-Rodino Antitrust Improvements] Act has passed," Alaska Airlines announced in a statement. "This marks a significant step in the process of joining our airlines."

In January, the DOJ won a court ruling that prevented 's acquisition of . Additionally, the DOJ won another suit in 2019 that reversed a partnership between JetBlue and in the Northeast.

The deal between Hawaiian Airlines and United Airlines was announced in December, after Hawaiian had faced challenges such as the Maui wildfires, increased competition from Southwest Airlines, and a slower recovery of travel to and from Asia due to the Covid-19 pandemic.

Since the beginning of 2020, Hawaiian has recorded net losses in all quarters except one, but executives have stated that booking trends are improving. Hawaiian's stock price increased by almost 12% this quarter, as of Monday, while most other airlines' shares have decreased.

In December, the two airlines announced that they would maintain their brand identities while operating under a unified platform, resulting in a fleet of more than 360 planes covering over 130 destinations.

The Justice Department and Transportation Department didn't immediately comment on Tuesday.