On Monday, Alaska Airlines announced that its planned merger with Hawaiian Airlines has overcome a key regulatory hurdle set by the U.S. Department of Justice. This news came shortly after the airline agreed to prolong the review duration for the $1.9 billion agreement.

The news led to a nearly 9% rise in Hawaiian Airlines’ stock during premarket trading on Tuesday, while Alaska Airlines’ shares remained unchanged.

“The timeframe for the U.S. Department of Justice to carry out its regulatory review of the proposed merger of Alaska Airlines and Hawaiian Airlines under the HSR Act has concluded,” Alaska Airlines stated on its website.

The airline mentioned it was now waiting for the next steps from the U.S. Department of Transportation.

Alaska Airlines, which revealed the merger plans last year, had recently agreed to extend the review period of its acquisition proposal regarding Hawaiian Holdings with the DOJ.

“Today marks a significant milestone for the potential merger of Alaska Airlines and Hawaiian Airlines, as the regulatory review period by the U.S. Department of Justice has finished,” stated Hawaii’s Governor Josh Green.

“This merger will tremendously enhance the number of non-stop or one-stop destinations available for Hawaii residents across North America, and HawaiianMiles members will keep the value of their miles while gaining access to additional global destinations.”

The aviation sector has seen rigorous evaluations of mergers and acquisitions by regulators. Earlier this year, the planned $3.8 billion acquisition of low-cost carrier Spirit Airlines by JetBlue Airways was blocked by a federal judge.