Allegiant already flies into many major airports, including McCarran International (Las Vegas) and Fort Lauderdale-Hollywood International Airport. In June 2013, Allegiant deviated from this strategy with plans to compete with Southwest Airlines by offering direct flights between Las Vegas and Austin, a medium hub served by 10 carriers with non-stop routes to over 40 destinations. The airline also flies less frequently compared to the major airlines, operating routes two or three times per week. That requires fewer crews and allows less time-pressured aircraft maintenance.
On June 22, 2009, Frontier Airlines announced that pending bankruptcy court approval, Republic Airways Holdings, the Indianapolis-based parent company of Republic Airlines, would acquire all assets of Frontier Airlines for the amount of $108 million. Thus, Frontier Airlines would become a wholly owned subsidiary of Republic. However, 5 weeks later on July 30, Dallas-based Southwest Airlines announced that it would be making a competing bid of $113.6 million for Frontier with intentions to also operate Frontier as a wholly owned subsidiary, but that it would gradually fold Frontier resources into current Southwest operating assets.
In December 2015, the FAA issued a letter of correction due to an incident where an Allegiant aircraft attempted to fly to Hector International Airport in Fargo, ND in late July 2015, which was at the time within a temporary flight restriction due to a rehearsal by the Blue Angels flight team for an upcoming air show in Fargo respectively. The pilots flying the aircraft then declared a fuel emergency stating, "Yeah, listen, we're bingo (empty) fuel here in about probably three to four minutes and I got to come in and land." The pilots were scolded by the airport's tower who said, "Your company … should have been aware of this for a number of months," regarding the airspace restrictions which would have prevented flight to the airport. The pilots flying the aircraft were, at the time, the airline's vice president of flight operations and its director of flight safety.
The company had charter contracts with Caesars Entertainment to ferry customers to Caesars casino properties through Reno-Tahoe International Airport, Laughlin/Bullhead International Airport and Tunica Municipal Airport. These contracts ended in December 2012 when Caesars Entertainment signed a new contract with Republic Airways to provide the charter service to Caesars properties in Atlantic City, New Jersey, Tunica, Mississippi and Laughlin, Nevada.
In December 2006, jetBlue, as part of their RTP plan, removed a row of seats from their A320s to lighten the aircraft by 904 lb (410 kg) and reduce the cabin crew size from four to three (per FAA regulation requiring one flight attendant per 50 seats), thus offsetting the lost revenue from the removal of seats, and further lightening the aircraft, resulting in less fuel burned.
Allegiant Air has been closely monitored by the FAA due to many emergency landings and aborted takeoffs. ABC interviewed a former Allegiant mechanic, who said "Dedicated steps were not being performed with maintenance manuals or even with general practices, before an aircraft is released." Many of these incidents had involved Allegiant's aging MD-80 aircraft, which as of November 2018 have been replaced by newer Airbus A320 family aircraft. 46 of the 86 aircraft have made emergency landings, all of which were on MD-80s. The average age of Allegiant's MD-80 fleet was 29 years compared to less than 13 years for its Airbus fleet.
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.
In May 2017, Allegiant Air took delivery of its first brand-new A320. Allegiant took delivery of ten new A320s in 2017 and is scheduled to accept two in 2018. All new aircraft will be painted in Allegiant's new livery at the time it is delivered. Older Airbus aircraft will be repainted during their C-checks. The new Airbus aircraft will have fuel-efficient sharklets. The new A320s seat 186 passengers, an increase of the 177 seats that are found in the rest of the Allegiant A320 fleet. To fit the additional nine seats, Allegiant opted for the Airbus Space-Flex V2 Lavatory. 
Allegiant Air (G4) is an American low-cost carrier that is headquartered in a suburb of Las Vegas. Founded in 1997, the airline does not use hubs, but has designated more than 10 focus cities. These include McCarran International Airport (LAS), Fort Lauderdale–Hollywood International Airport (FLL), Los Angeles International Airport (LAX) and Orlando Sanford International Airport (SFB). Although Allegiant flies into some major airports, many of its destinations are smaller cities or secondary airports that serve larger cities. In total, the airline serves about 105 domestic destinations in 41 states. The airline's fleet of 81 aircraft are each configured with a single Economy Class cabin.