But most budget airlines use aircraft such as the 737 and A320 which are also the most prevalent aircraft in the big airlines. They don't really use smaller aircraft than traditional airlines, they just don't use as many big aircraft.

Budget and "Ultra-Low-Cost Carriers" (ULCCs) overwhelmingly use a single-type fleet strategy centered on two aircraft families: the Boeing 737 and the Airbus A320. In 2026, the most common models are the Boeing 737-800 and the newer, high-density 737 MAX 8-200 (a favorite of Ryanair), as well as the Airbus A320neo and A321neo (widely used by Spirit, Frontier, and Wizz Air). By using only one type of aircraft, budget airlines drastically reduce costs for pilot training, maintenance, and spare parts. These planes are typically configured with "high-density" seating, often featuring 189 to 230 seats in an all-economy layout with reduced legroom (pitch). For long-haul budget flying, a few carriers like French bee or Cebu Pacific utilize the Airbus A350 or A330neo, but they still maintain the high-density philosophy. The strategy is simple: maximize the number of passengers per flight while minimizing the operational complexity of the fleet. This uniformity is what allows these airlines to offer $19 base fares while maintaining a relatively young and fuel-efficient fleet of narrow-body jets.