The ruling is a major victory for the Biden administration, which has used aggressive enforcement of antitrust laws to fight against mergers and other arrangements between large corporations.
The Biden administration sued on Tuesday to block the $3.8 billion purchase, saying the deal would reduce competition and drive up air fares for consumers.
NPR's Leila Fadel speaks with Diana Moss, president of American Antitrust Institute, about actions the Department of Justice may take to block the Spirit Airlines-JetBlue merger.
The agreement Thursday capped a months-long bidding war and arrives one day after Spirit's attempt to merge with Frontier Airlines fell apart. The deal still needs approval from antitrust regulators.