DALLAS—A federal judge on Tuesday sided with the Biden administration and blocked JetBlue Airways from buying Spirit Airlines, saying the $3.8 billion deal would reduce competition. The Justice Department had sued to block the merger, saying it would drive up fares by eliminating Spirit, the nation’s biggest low-cost airline. U.S. District Judge William Young, who presided over a non-jury trial last year, said Tuesday that the government had proven that the merger “would substantially lessen competition” and violated a century-old antitrust law. In his ruling, which ran more than 100 pages, the judge gave a nod to the Justice…
