In May 2005, the airline's holding company, Allegiant Travel, completed a private equity placement worth $39.5 million that was funded by the investment firms of ComVest and Irelandia II. In November 2006, Allegiant filed a registration statement with the Securities and Exchange Commission in anticipation of a planned initial public offering of its Common Stock. It raised $94.5 million in equity capital with 5.75 million shares worth $18 each. It began trading on the NASDAQ Stock Market under the ticker symbol "ALGT" in December 2006.
In December 2016, a winter weather event disrupted fleet operations, causing Frontier to delay or cancel up to 70% of their flights during the peak of the crisis, many without any advance notice. On the weekend of December 17, the storm caused major delays at Frontier's Denver hub, and the effects of the storm were felt throughout the fleet. Flights were delayed or canceled at airports across the country, as in some cases, planes were ready to depart, but there were no rested flight crews available to service the flight. The head of Frontier's pilot's union issued a statement criticizing the companies' handling of the event, comparing the airline to a "house of cards". Frontier received over 30,000 refund requests for canceled flights resulting from the event.
Dave Siegel took the chief executive officer role in January 2012. Siegel's tenure ran through May 2015, when he left for personal reasons and was succeeded by the company's chairman, Bill Franke, who would manage strategy and finances. In April 2014, Barry L. Biffle was appointed as the company's president, reporting to Siegel; after Siegel's departure, Biffle was charged with managing the company's day-to-day operations.
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.
In 2009, jetBlue announced that it was looking for a new headquarters location, and was considering moving either within the New York City metropolitan area or to the Orlando, Florida area. In April 2009, Helen Marshall, the president of the Borough of Queens, said that the City of New York was trying to keep JetBlue in the city; in January 2010, the CEO of JetBlue, Dave Barger, and Governor of Florida Charlie Crist met in Tallahassee, Florida to discuss a possible move to Orlando. A decision was expected by March 2010, although a move would not happen until 2012, when its lease in the Forest Hills Tower expired.
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 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 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.
As jetBlue gained market share, they found a unique positioning where they competed with other low-cost carriers (e.g. Southwest, and Frontier), as well as major carriers (e.g. American, United, and Delta). Amenities such as their live in-flight television, free and unlimited snack offerings, comfortable legroom, and unique promotions fostered an image of impeccable customer service that rivaled the major airlines, while competitive low fares made them a threat to low-cost no-frills carriers as well.
In February 2012, Frontier Airlines cut five nonstop routes from Milwaukee. This move "reduced Frontier's daily departing flights out of Mitchell International from 32 to 18," or 56%. Frontier announced further layoffs in conjunction with this route change: up to 446 Milwaukee-area employees were affected by the job cuts that occurred between April 15 and April 30, 2012.
In 2013, Allegiant acquired nine Airbus A320-200 aircraft from Spanish flag carrier Iberia. Seven of the A320s were delivered in 2013 and were used for growth into new markets, including destinations in Mexico and the Rocky Mountains, as well as airfields such as Charlottesville and Shenandoah Valley in Virginia and Trenton, New Jersey. On February 24, 2015, Allegiant announced the purchase of 2 additional A320s from Philippine Airlines which entered into service in 2015. Later in 2015, the airline announced a firm order for an Airbus A320 direct from Airbus, the first time it has purchased new aircraft from the supplier.
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. 
I just had horrendous experience and customer service! I booked a round trip flight for my son from Stockholm to Zurich via Amsterdam. It was 185 USD. Travelocity emailed us on the day of the flight that the flight from Amsterdam to Zurich and all return flights were cancelled. My son ended up booking a new flight from Stockholm to Zurich that costed him about 500 USD. I reached out Travelocity customer service via Facebook. The rep admitted that email was an error but ensured me that return flight was still good. However, my son was charged 285 USD penalty on the return flight for missing the first leg. In the end, he ended up paying 800 USD out of his pocket. Short flight cost us a total of 1000 USD! The reps via Facebook said they were sorry but they would not do anything to compensate/reimburse me or be accountable for their mistakes. I will NEVER use Travelocity again for sure!!
Various consumer rights organizations and activists called for the creation of a government mandated “Bill of Rights” to protect air travelers from future experiences similar to the one previously described. On February 20, 2007, jetBlue released an apologetic response to the events that had taken place less than a week before with the creation of their Customer Bill of Rights, which offers financial reciprocation if a customer's flight is delayed or cancelled.
In 2008, jetBlue partnered with Irish flagship carrier Aer Lingus to allow passengers to switch between airlines on a single ticket for flights with connections in New York–JFK or Boston Logan. Unlike traditional codeshare agreements, the companies cannot sell seats on each other's flights, so customers initiate the purchase on one airline's website and then are transferred to the other site to complete the transaction.