CHICAGO—JetBlue Airways Corp. on Monday ratcheted up its bidding war with Frontier Group Holdings for Spirit Airlines Inc. as the race for the ultra-low-cost carrier enters the final stretch.
Both bidders see Spirit as an opportunity to expand their domestic footprints at a time when the U.S. airline industry is dogged by labor and aircraft shortages. Either of the deals would create the fifth-largest U.S. airline.
