The Justice Department is expected to decide soon whether to file a lawsuit to block the JetBlue-Spirit Airlines merger, and some antitrust advocates are hoping they will take that legal action.

The Department of Justice had an initial deadline of Feb. 28, but has not yet decided on a legal course of action.

In October, Spirit shareholders voted to accept JetBlue's $3.8 billion hostile takeover bid for the ultra low cost carrier, beating out another ULCC, Frontier, for the airline. The deal was expected to close on Tuesday, but the airlines have agreed to a brief delay.

If the merger wins regulatory approval and is finalized, the combination of JetBlue and Spirit would create the 5th largest airline in the U.S., with about 10% of the domestic market share.

But antitrust regulators in the Biden administration have raised concerns about the deal, as consumer advocates say it would reduce competition in the air travel market, leading to fewer choices for travelers and higher fares.

Late last month, JetBlue and Spirit Airlines made a last-minute attempt to win Justice Department support, arguing that a merger would lower ticket prices across the industry.

Robin Hayes, JetBlue CEO, and Ted Christie, Spirit Airlines CEO, met with the leaders of the Justice Department's antitrust division where they described their vision to secure low fares within the merger company.

If the companies merge, JetBlue says it would reconfigure the interior of Spirit's planes in an effort to increase legroom. To keep fares low, Spirit maintains high passenger capacity on its planes. JetBlue plans to spread the rows between seats a little farther apart, to mirror its seat configuration. This would decrease the number of seats on Spirit's airplanes, which would normally force an increase in fares, but JetBlue and Spirit officials say this will not be the case, arguing that their combined airline will be more efficient with planes spending more time in the air and less time on the ground.

The airlines also argue the merger will be good for competition, for greater efficiency will allow them to fly to more destinations, which will lower prices, too.

Diana Moss, the president of the American Antitrust Institute, an organization that promotes competition to protect consumers and businesses, argues that the merger will affect airline competition. She says a lack of competition will weaken the airline industry and make it harder to work through unforeseen circumstances, like disastrous weather and COVID.

Moss also says the merger will harm workers, but some airline unions support the JetBlue-Spirit merger. Traditionally, labor unions do not support major airline mergers, but this time some labor unions say this merger will benefit workers and consumers.

"Our union has experience with eight mergers in the past ten years," says Sara Nelson, president of the Association of Flight Attendants-CWA.

"The JetBlue-Spirit merger adds competition to the airline industry that creates more power for workers, along with choice and comfort that benefits consumers. We urge regulators to work diligently to ensure the financial merger closing occurs in the near term so that Flight Attendants, other workers, and consumers can access the benefits of the merger as soon as possible."

The union says the merger will also create more competition against four airlines that currently occupy 81% of the aviation industry, American, Delta, Southwest and United. Spirit flights attendants say they are looking forward to the modified airplanes.

Although some flight attendants support the merger, consumer groups like the American Economics Liberties Project argue that the merger will reduce competition and flights, cut workers and increase the average price of airfares across the nation. As the debate continues, workers and consumers anticipate the Justice Department's decision.

Morning Edition's Leila Fadel recently spoke with Diana Moss about the actions the Department of Justice might take to block the Spirit Airlines-JetBlue merger. She says she believes competition is a top factor in this debate.

This interview has been edited for length and clarity.

Interview highlights

On the negative effects of mergers

Mergers can affect labor by reducing bargaining power of pilots and other airline workforces, and it's one less competitor in our passenger aviation system. So losing an important competitor can really contribute to having sort of a fragile system that isn't very resilient to withstand shocks, like what we saw with weather at the end of 2022 and even COVID.

What happens with these types of joint ventures is, the more expensive workforces are displaced with the lower, the less expensive workforces. But that in itself is not necessarily a bad thing. But when it results from a joint venture, for example, eliminating competition, that's when we start to worry.

On airline competition

We're really looking at how on important routes from origins to destinations, how the merger will affect competition, and it really does eliminate an important competitor. And when you have that in markets where there isn't a lot of competition anyway, as a result of many, many years of consolidation, then that really does start raising questions about higher fares and lower quality for consumers. We maintain important resiliency in our air system by having more competition instead of less.

On how the DOJ could respond

The Biden administration is committed to promoting competition and slowing down the kind of consolidation that we've seen in the U.S. economy for many years. And the only way to do that really is for the DOJ to evaluate the merger, to file a lawsuit on the grounds that it's illegal and it would really substantially reduce competition.

Depending on how the airlines want to respond to that, there could be a settlement. We do not favor a settlement because we don't think that would really restore competition or they could end up in federal court litigating this case in front of a judge. I think that is probably the best way to ensure that consumers are not harmed by this merger and that workers, various labor forces are not harmed, and that we maintain important resiliency in our air system by having more competition instead of less.

David Schaper contributed reporting.