In the fall of 2001, Allegiant exited bankruptcy and the case was officially closed in early 2002. In March 2002, Allegiant entered into a long-term contract with Harrah's to provide charter services to its casinos in Laughlin and Reno, Nevada. At the same time, the airline acquired its first McDonnell Douglas MD-80 jetliner. From 2002 through 2004, the airline developed its scheduled-service business model. By 2004, Allegiant was flying from 13 small cities to Las Vegas offering bundled air and hotel packages.
The airport director in Worcester, Massachusetts, felt that Allegiant reneged on a commitment to serve the airport for five years given the use of federal grants to assist its startup. However, the airline responded that the market was immediately unprofitable and starting service there was a poor decision; flights were reported to be 80% full. Allegiant's flights average 90% full.
That's why I decided to use it again for our Rosarito getaway on Labor Day weekend. Found a less than fancy hotel at an amazing price of $53, taxes and breakfast included. It was perfect for our needs, as we were only staying one night, and sleep only for a few hours at that. I ignored all the bad reviews of the hotel being dirty and unsafe, but I never imagined that so much worse awaited us. When we arrived, they told us that they were full and that there was no record of our reservation to begin with. How did that even happen? And if the hotel had been full since Friday, how did it allow me to do the reservation on Thursday? I couldn't reach them in Mexico. By the time I was able to talk to someone we were already in the United States and unable to take an alternative room. We only had one night, I didn't want to waste it looking for hotels when we had already checked two others at a way higher price. The only reason we went out there is for the amazing advertised price, the price I thought we had locked in through a reservation. But no way was I going to fall in that game of taking a more expensive room out of desperation. We just left. Drove back all the way to L.A.
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 International Airport and Stockton several times a week; however, there is no service at present flown between these two cities although Allegiant continues to serve Stockton with flights to Las Vegas, Phoenix/Mesa and San Diego. In November 2011, Allegiant closed its Long Beach facility and consolidated all Los Angeles area flights at Los Angeles International (LAX).
Frontier was ranked in an airline quality rating report by Embry-Riddle Aeronautical University and Wichita State University in 2015 as one of the five worst airlines in the United States, especially due to its rate of customer complaints and bumped passengers. The airline also had relatively poor on-time performance, and the waiting time for help when calling the airline on the phone was reported to have risen to two hours or more.
In April 2010, Allegiant purchased six Boeing 757-200 aircraft from Thomson Airways for flights to Hawaii with the delivery of the first two in the following months. In September 2011, Allegiant Air introduced the 757 into service from their main hub in Las Vegas. Allegiant later began using the ETOPS configured 757s for service to Hawaii. Fresno and Las Vegas were the inaugural destinations with nonstop service to Honolulu, Hawaii. Nonstop service to Honolulu was then added from Bellingham, Boise, Eugene, Phoenix (via Mesa Gateway Airport), Santa Maria, Spokane and Stockton. Nonstop service to Hawaii was also planned from Monterey, CA but was not actually operated. Allegiant then began to reduce its Hawaii service after determining that the extensive and costly maintenance check - which happens about every six years and costs upwards of $1 million - would not be efficient on the aircraft they flew to Hawaii.
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 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.