Federal antitrust enforcers are preparing to file a lawsuit seeking to block JetBlue Airways’ proposed $3.8 billion acquisition of Spirit Airlines.

The deal, announced in July of 2022 after JetBlue topped a rival bid for Spirit from Frontier Airlines, would create the fifth-largest carrier in the U.S. 

Lawyers for the U.S. Department of Justice could move to halt the transaction as early as Tuesday, CBS News confirmed. 

A spokesperson for the agency declined to comment.

Robin Hayes, CEO of New York-based JetBlue, said the airline is disappointed, but not surprised, by the government’s potential lawsuit. 

“We’re not taken aback. We had already stated last year, when we received approval from Spirit shareholders, that we didn’t anticipate closing the deal in the first half of 2024. It’s a legal matter,” he told “CBS Mornings” on Tuesday.

JetBlue is expected to fight a Justice Department suit in court.

Hayes has said that combining JetBlue and Spirit, a Florida-based discount carrier, would spur competition in the airline industry. In defending the merger, JetBlue said Monday that the two airlines mostly compete with other major carriers, notably American Airlines, Delta Air Lines, Southwest Airlines and United Airlines. JetBlue and Spirit overlap on no more than 11% of their respective nonstop routes, according to JetBlue.

The combined airline would have a fleet of roughly 460 aircraft and would add more than 1,700 daily flights to more than 125 destinations in 30 countries, JetBlue said last year. Together, the companies would have 9% of the market, compared with the 16% to 24% share held by each of the four largest airlines, JetBlue added. 

“This is not Pepsi buying Coke,” Hayes said, adding that “JetBlue and Spirit together will be 8% or 9%” of the market for air travel in the U.S. “Most people are still going to be flying on the other airlines. That’s where you’re going to save the really big dollars — by having a bigger JetBlue.”

JetBlue’s Spirit purchase has also faced opposition from other quarters. A coalition of consumers and flight attendants in November sued to stop the deal on grounds it would let the combined carrier dominate certain routes, according to Bloomberg Law.

The Justice Department, along with six states and the District of Columbia, in 2021 also sued to block JetBlue and American from consolidating their operations in Boston and New York City, arguing that it would harm competition.

CBS News’ Jeff Pegues and Analisa Novak contributed to this report.