US carriers JetBlue and Spirit filed an appeal in federal court Friday seeking to reverse a judge’s decision to block their planned merger. The airlines “hereby appeal to the United States Court of Appeals for the First Circuit” against Tuesday’s ruling in Boston, according to a notice of appeal filed with the court. The merger, if ultimately approved, would create the fifth-largest airline in the United States. US District Judge William Young rejected the plan earlier this week after the Justice Department last year sued to block the merger, noting the move would hurt consumers and violate antitrust law. Lawyers for the airlines had argued that the tie-up stands to benefit customers “by bringing low fares and great service” to more markets, and would boost their ability to compete with dominant US carriers. But President Joe Biden and US Attorney General Merrick Garland instead called Young’s ruling a “victory” for American consumers. JetBlue’s bid to acquire low-cost Spirit was announced in July 2022 after several months of twists and turns in the volatile airline industry, with JetBlue’s offer of $3.8 billion prevailing in a bidding war with competitor Frontier. Should the merger go through, the new entity would rank behind the “big four” — American, United, Delta and Southwest airlines — in number of seats offered. According to figures provided by JetBlue and Spirit at the time, it would hold roughly a nine percent share of the US market.