The airline tends to offer lower fares, which requires strict cost control. Part of the airline's lower cost structure included operation of McDonnell Douglas MD-80 jets, which the airline can purchase and refurbish for as little as $4 million. While the aircraft are less fuel-efficient than newer planes, Allegiant was able to purchase used MD-80s outright for one-tenth the cost of a new Boeing 737 although Allegiant has subsequently purchased used Boeing 757-200s, Airbus A319s and Airbus A320s. (The 757s were acquired for its Hawaii service while the Airbus jets were beginning to replace MD-80 aircraft). As of November 2018, however, Allegiant no longer operates any MD-80 aircraft, relying instead on an all-Airbus fleet. Given the low cost of ownership, Allegiant is able to operate its aircraft less (seven flight hours per day on average versus 13 hours per day at JetBlue Airways), which helps keep labor costs lower. Overall, Allegiant operates with 35 full-time workers per plane compared to more than 50 at other carriers. Allegiant schedules their crew members so that they always return to their domicile at the end of the day, thus avoiding the need for hotel rooms which can be a costly expense for airlines.
In March 2010, Allegiant purchased six used Boeing 757-200 jetliners as part of plans to begin flights to Hawaii, with deliveries from early 2010 to the fourth quarter of 2011. It gained the approval for type with the FAA in July 2011, and then worked with the FAA to obtain the appropriate ETOPS rating in order to be able to serve Hawaii. Allegiant no longer operates nonstop service to Honolulu from Las Vegas.
The initial JetExpress partnership with Mesa ended in January 2004, when Horizon Air was selected to operate the routes. Horizon utilized slightly larger CRJ-700 regional jet aircraft on these routes. In August 2006, Frontier and Horizon ended their partnership. While Frontier was generally pleased with Horizon's operation, the carrier decided that it needed to revisit the agreement and find a provider with additional regional jets to grow the operation. The last of the CRJ-700's was returned to the Horizon Air fleet on November 30, 2007.