after Alaska Air agreed to buy the rival airline for $1.9 billion, including debt.

The deal comes after Hawaiian shares had lost more than half their value this year due to the impact of the Maui wildfires, high fuel costs, and jet engine recall issues for some of its planes.

Alaska and Hawaiian said on Sunday that the deal will expand their networks and offer more choices to passengers.

One analyst told Reuters the deal will enable Alaska to grow in the lucrative Asia Pacific market, while Hawaiian customers can travel non-stop to the U.S. mainland, with minimal further investment.

However, regulatory resistance to the merger is a possibility.

The U.S. Justice Department filed a lawsuit in March to stop JetBlue from buying Spirit Airlines, saying the planned merger "would put travel out of reach for many cost-conscious travelers".

Shares of Alaska Air ended down more than 14% at Monday's close.