Spirit Airlines and Frontier Airlines, two prominent budget carriers, announced plans to merge on Monday, a combination that would create the fifth-largest U.S. airline by market share, putting pressure on the nation’s biggest carriers and raising concerns about further consolidation in an already-concentrated industry.The airlines, which offer 1,000 daily flights serving destinations in the United States, the Caribbean and Latin America, said in a statement that they would save $1 billion annually from the merger, without layoffs. They also said they expected to hire another 10,000 workers by 2026 to add to their combined 15,000 employees currently.The deal could face pushback from the Biden administration, which has increasingly challenged such combinations in court. In the fall, the Justice Department sued to prevent a domestic alliance …
