Alaska Airlines said Wednesday it had agreed to extend by a day the review period of its proposed $1.9 billion acquisition of peer Hawaiian Holdings.

Alaska and Hawaiian agreed with the U.S. Department of Justice to extend the review period until Friday, Seattle-based Alaska Airlines disclosed in a filing.

Last month, the airlines said the review period was extended to today.

The deal was announced last year and the carriers said in March they “have been working cooperatively with the DOJ and expect to continue to do so.”

The shortage of new aircraft worldwide has made airlines turn to mergers and acquisitions to expand capacity and market share.

The deal would give Alaska control of more than half of the market for flights to Hawaii, one of the world’s top holiday destinations.

However, such deals have faced tough scrutiny from regulators. Earlier this year, a federal judge blocked JetBlue Airways’ planned $3.8 billion acquisition of ultra-low-cost carrier Spirit Airlines.