Frontier Airlines

Frontier Airlines occupies the ultra-low-cost carrier space in the US domestic market alongside Spirit, but earns higher placement on this list due to a significantly better customer experience and cleaner pricing structure in 2025-2026. Frontier DISCOUNT DEN membership ($59.99/year) unlocks the lowest fares on the network — often $20-40 for routes that United and Delta charge $150+. The aircraft (Airbus A320neo family) are modern, fuel-efficient, and equipped with full-size seatback screens that Spirit and Allegiant lack. Frontier new bundling approach (introduced 2024) makes the total cost more predictable: the Premium bundle at $79 extra includes checked bag, carry-on, seat selection with extra legroom, and priority boarding. For budget-conscious domestic US travelers flying routes where Frontier operates (primarily connecting secondary cities to Denver, Orlando, Las Vegas, and Atlanta hubs), the value proposition is genuine.