This article discusses the U.S. Department of Justice's decision to file a lawsuit to block JetBlue's proposed $3.8 billion acquisition of Spirit Airlines, a move that would create the fifth-largest carrier in the U.S. The lawsuit is seen as a test of President Joe Biden's aggressive antitrust strategy, and the Transportation Department is also expected to deny a transfer of Spirit's airline certificate. JetBlue CEO Robin Hayes expressed disappointment but not surprise at the government's determination.