The Justice Department sued Tuesday to block JetBlue Airways' $3.8 billion purchase of Spirit Airlines. 

The department said the merger would reduce competition and drive up fares for consumers. 

Specifically, the department asserted that the deal would hurt cost-conscious travelers who depend on Spirit to find cheaper fares. 

JetBlue and Spirit have expected the challenge for weeks and negotiations over a possible settlement failed. 

JetBlue CEO Robin Hayes told "CBS Mornings" on Tuesday that he was disappointed but not surprised by the lawsuit. 

"We said when we got the offer approved by the Spirit shareholders last year that we didn’t think we would close until the first half of 2024, expecting a trial," he said.

JetBlue and Spirit executives argued that the merger would help consumers by creating a stronger competitor to the four carriers that control about 80% of the domestic air-travel market.

Attorney General Merrick Garland is holding a news conference at 11:30 a.m. EST to announce the lawsuit. 

The Associated Press contributed to this report.