Allegiant Air

2010s

In January 2010, the airline celebrated its one-millionth passenger to fly out of Phoenix-Mesa Gateway Airport. Allegiant's parent company also announced that it had purchased 18 additional used MD-80 aircraft from Scandinavian Airlines. In February 2010, Allegiant opened its ninth base at Grand Rapids' Gerald R. Ford International Airport in Michigan. The airline based two McDonnell Douglas MD-80 aircraft in Grand Rapids, but ended their airport's status in 2011. The airline continues to fly out of Grand Rapids in a reduced capacity.

On July 1, 2010, Allegiant returned to Long Beach Airport (LGB) in Long Beach, California, having previously served LGB with DC-9 jets with nonstop flights to Las Vegas (LAS) and Lake Tahoe (TVL) in 2000. The airline also intended to fly from Bellingham and Stockton several times a week; however, that plan never came to fruition. Allegiant continues to serve Stockton with flights to Las Vegas, Phoenix/Mesa and San Diego. About 16 months later in November 2011, Allegiant closed its Long Beach facility.

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 approval for the 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 service to Hawaii.

In July 2015, Allegiant Air announced that bases would be established at the Asheville Regional Airport and Cincinnati/Northern Kentucky International Airport. In October the same year, it came under Federal Aviation Administration monitoring following several emergency landings and aborted takeoffs involving its McDonnell Douglas MD-80 fleet. In December, WFTS-TV interviewed a former Allegiant mechanic who alleged that maintenance procedures were not consistently followed before aircraft were returned to service. A 2016 investigation by the Tampa Bay Times reported that Allegiant aircraft were four times more likely to experience in-flight failures than aircraft operated by other major U.S. airlines. The newspaper also found that 46 of the airline's 86 aircraft had made emergency landings. At the time, the average age of Allegiant's MD-80 fleet was 29 years. There were also more than 100 serious mechanical incidents between January 2016 and October 2017, including engine failures, cabin smoke incidents, hydraulic leaks, and aborted takeoffs. Allegiant responded that many of the incidents involved its MD-80 fleet, which it was replacing with Airbus A320 family aircraft. The airline also cited the 2016 FAA audit, which found the carrier's safety issues to be "minor" and "non-systemic". Allegiant later stated that it received a "clean bill of health" following a 2016 FAA audit. FAA officials said the airline had returned to the agency's normal five-year inspection cycle.

In August 2017, Allegiant announced that a new base would be established at the Indianapolis International Airport. The base began operations in early 2018. Throughout 2017, the airline flew 12 million passengers on its 99 planes to 120 destinations from California to Florida. In February 2018, Allegiant also announced that a new base would be established at the Destin–Fort Walton Beach Airport. In June 2018, Allegiant added another base at McGhee Tyson Airport in Knoxville, Tennessee. Allegiant retired all of its MD-80 aircraft by November 2018.

In January 2019, Allegiant announced that it would be adding another base at Gerald R. Ford International Airport in Grand Rapids, Michigan. Allegiant announced that they would be adding an additional base at Des Moines International Airport in Des Moines, Iowa, by November 2019. The base was delayed as a result of the COVID-19 pandemic and opened in 2021.

2020s

On February 12, 2021, Allegiant launched flights to John Wayne Airport in Orange County, California with eight initial destinations including Boise, Grand Junction, Las Vegas, Medford, Missoula, Provo, Reno/Tahoe, and Spokane.

On August 10, 2021, Allegiant announced that they would be opening two more operating bases at Appleton and Bishop beginning March 2022.

On October 7, 2021, Allegiant began serving non-stop flights from Minneapolis-St. Paul to Asheville, North Carolina, and Palm Beach, Florida. They would later serve five more, including Punta Gorda, Florida; Destin-Fort Walton Beach, Florida; and Phoenix-Mesa, Arizona. They serve all of these routes using Airbus A320 family aircraft. During the same year, it entered into a joint venture with Viva Aerobus to expand routes between the United States and Mexico.

In January 2026, Allegiant Travel Company announced an agreement to acquire Sun Country Airlines in a cash-and-stock transaction valued at about $1.5 billion. The agreement was approved by the boards of both companies and expected to close in the second half of 2026, subject to approval by Sun Country shareholders and regulatory review by the United States Department of Justice and other authorities. The airlines will continue to operate separately until receiving a single Federal Aviation Administration operating certificate. Following the completion of the merger, the combined airline was expected to operate under the Allegiant name and be headquartered in Las Vegas, with Allegiant chief executive officer Gregory C. Anderson continuing to lead the company and Sun Country chief executive officer Jude Bricker joining the board of directors.

Fleet development

Allegiant has historically pursued a lower-cost fleet strategy by purchasing used or discounted aircraft and operating them at lower daily utilization rates than many competitors. The company has stated that low acquisition costs allow it to operate aircraft profitably at lower utilization rates than many other airlines. Allegiant aircraft average between 4+1⁄2 and 8 flight hours per day, compared with the 11 hours per day targeted by Frontier, another U.S. ULCC, and 13 hours at carriers such as JetBlue.

At the start of operations in the late 1990s, Allegiant operated used McDonnell Douglas DC-9 aircraft. In 2002, the airline began replacing the DC-9 fleet with newer used aircraft from the McDonnell Douglas MD-80 family (MD-82, -83, -87, and -88), a later derivative of the DC-9.

Starting in 2010, Allegiant purchased six Boeing 757-200 aircraft from Thomson Airways. The airline used the aircraft to launch service between the mainland United States and Hawaii. The Hawaii service was ultimately discontinued, and the airline gradually retired the 757 fleet by the end of 2017 rather than undertake expensive D checks on the aircraft.

In 2012, Allegiant announced a transition from the MD-80 fleet to the Airbus A320 family. The airline purchased 35 used Airbus A319 aircraft from EasyJet and Cebu Pacific, configured with high-density seating and four overwing exits. Beginning in 2013, the airline also added used Airbus A320 aircraft acquired from airlines including Iberia and Philippine Airlines, while leasing additional aircraft.

In 2016, Allegiant purchased its first brand-new aircraft, ordering 13 Airbus A320s directly from Airbus. The airline stated that it took advantage of lower prices as Airbus prepared to transition production to the newer A320neo family. After exercising additional purchase options, Allegiant ultimately acquired 29 new Airbus aircraft.

The airline retired its last MD-80 in November 2018.

In January 2022, Allegiant announced an order for 50 Boeing 737 MAX aircraft. The airline plans to retire its oldest Airbus aircraft, but will continue to operate the A320-family aircraft alongside the 737 MAX fleet.