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.
In July 2012, Allegiant announced the future addition of the Airbus A319-100 aircraft to its fleet. The aircraft are used and formerly belonged to easyJet and Cebu Pacific. All of them are high-density A319s, fitted with four overwing exits, allowing 156 seats. Two former easyJet aircraft entered service in 2013, with another in 2014 and an additional six in 2015. In December 2012, Allegiant cancelled the agreement with Cebu Pacific citing an inability to agree on economic provisions. On May 1, 2013, Allegiant purchased another A319 aircraft previously operated by easyJet that would enter service in the third quarter of 2013. On February 23, 2015, Allegiant purchased six more A319s from Cebu Pacific.
Although it does not fly to Canada, Allegiant advertises extensively there and flies from about a dozen small airports near the Canada–US border. Many of its customers at airports such as Bellingham, Washington (BLI), Niagara Falls, New York (IAG), Ogdensburg, New York (OGS), Grand Forks, North Dakota (GFK) and Plattsburgh, New York (PBG) are Canadians, who can save money by flying from U.S. airports.
Frontier Airlines was the launch customer of the Airbus A318. Between 2003 and 2007, they took delivery of 11 of the type. However, retirement of the type already began in 2010 and was completed by autumn 2013. All of Frontier's A318 were not resold, but parted out for scrap. At the time of scrapping, the five youngest examples had spent less than two and a half years in active service, while the oldest two were just over ten years old.
As of April 2019, jetBlue Airways flies to 102 destinations in North, Central, and South America; including destinations in Aruba, The Bahamas, Barbados, Bermuda, Cayman Islands, Colombia, Costa Rica, Cuba, the Dominican Republic, Ecuador, Grenada, Haiti, Jamaica, Mexico, Peru, Puerto Rico, Saint Maarten, Saint Lucia, Trinidad and Tobago, Turks and Caicos Islands, and the United States.
In October 2013, Republic Airways Holdings entered into an agreement with private equity firm Indigo Partners to sell Frontier Airlines for approximately $145 million. According to Indigo, the transaction would further Frontier's evolution into an ultra-low-cost carrier. In December 2013, Indigo Partners LLC, through an affiliate, completed the purchase of Frontier Airlines from Republic Airways Holdings. The airline's headquarters will remain in Denver. Republic Airways Holdings subsidiary Republic Airlines no longer flies Embraer 190 aircraft on behalf of Frontier, as of January 1, 2014.
Frontier took delivery of its first Airbus aircraft (an A319) in 2001 and simultaneously launched with it DirecTV in-flight television along with a new company livery. Frontier Airlines was the launch customer of the Airbus A318 in 2003. In mid-April 2005, Frontier officially became an all-Airbus fleet, retiring its last Boeing 737.
In January 2008, Allegiant opened its sixth base at Washington's Bellingham International Airport. The airline bases two McDonnell Douglas MD-80 aircraft in Bellingham as part of the expansion. Routes served exclusively from Bellingham include Las Vegas, Palm Springs, San Diego, San Francisco and Phoenix. Expansion in Bellingham has been largely driven by its proximity to Greater Vancouver, British Columbia.
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.
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).