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 February 2011, Allegiant proposed to sell two types of tickets to passengers: advance tickets at a fixed higher rate and time-of-departure tickets that cost less but may have fees added based on the price of aviation fuel. In 2012, the U.S. Department of Transportation banned the practice as part of wider regulations that also require taxes and fees to be included in airfares. Allegiant, along with Spirit Airlines and Southwest Airlines, sued the DOT to overturn these new rules. The United States Court of Appeals for the District of Columbia Circuit ruled in favor of the DOT on 24 July 2012 and the US Supreme Court denied certiorari on 1 April 2013.
LIARS & SCAMMERS. Don't trust anything. Made a reservation for a rental car in Denver (Advantage) for a funeral trip. After waiting in line for an hour with only 3 agents helping a mass of people, the rental agent, "Aric," offered us a Yukon XL in place of the Camry we reserved. He said it was because we had waited in line for an hour and we were in Denver for a funeral. He said, "I'm going to give you guys a Yukon and free gas as well." We asked repeatedly if this would change the price because we didn't want to pay any extra. He told us to return the vehicle empty. He assured us more than once that this was just his gift to us and there would be no extra cost. He also added an additional driver also at no cost, so he said. The Yukon reeked of cigarette smoke and was very dirty but after waiting in line so long we just bought Febreeze and dealt with it ourselves. Aric made sure to ask us for a nice survey and recommendation when we got home as well. Our reservation was for $125.95 but we were charged $438.54!! Now wasting time fighting this. Unbelievable.
On January 11, 2007, Frontier Airlines signed an 11-year service agreement with Republic Airlines. Under the agreement, Republic was to operate 17, 76-seat Embraer 170 aircraft for the former Frontier JetExpress operations. At the time the contract was canceled in April 2008, Republic Airlines operated 11 aircraft for Frontier Airlines, with the remaining six aircraft expected to join the fleet by December 2008. With the integration of Republic aircraft, the 'JetExpress' denotation was removed. Subsequent to the cessation of Horizon's services for Frontier in December 2007, all flights operated by Republic were sold and marketed as "Frontier Airlines, operated by Republic Airlines." The first market created specifically for the Embraer 170 was Louisville, Kentucky, which began on April 1, 2007. Service to Louisville was suspended in August 2008 but restarted in April 2010.
In April 2013, Frontier introduced a modified version of that livery, keeping the iconic animals on aircraft tails, but dropping its former slogan and replacing "FRONTIER" with "FLYFRONTIER.COM", the company's website, in support of new marketing that focused heavily on the airline's web presence. This livery was only painted on a few newly delivered aircraft. Aircraft in the older livery received "FLYFRONTIER.COM" titles on engine nacelles.
JetBlue Technology Ventures (JTV)  is a wholly owned subsidiary of JetBlue that was established in February 2016. JTV is the venture capital arm of JetBlue that invests in and partners with early-stage startups in the travel, hospitality, and transportation space. Its mission is to improve the end-to-end experience of travelers everywhere. As of November 2018, JTV has invested in 21 startups, including hybrid planes, machine learning algorithms, and ground transportation. Investments range in size from $250,000 to $1 million.
jetBlue's first major advertising campaign incorporated phrases like "Unbelievable" and "We like you, too". Full-page newspaper advertisements boasted low fares, new aircraft, leather seats, spacious legroom, and a customer-service-oriented staff committed to "bringing humanity back to air travel". With a goal of raising the bar for in-flight experience, jetBlue became the first airline to offer all passengers personalized in-flight entertainment. In April 2000, flat-screen monitors installed in every seatback allow customers live access to over 20 DirecTV channels at no additional cost.
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).
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.
In summer 2015, a rash of midair breakdowns drew federal scrutiny. "Before the night was finished on June 25, 2015, five Allegiant flights had been interrupted in four hours, all because different planes had failed in midair," reported the Tampa Bay Times. Since October 2015, the Federal Aviation Administration has kept Allegiant under close supervision. In July 2015, Allegiant Air announced bases would be established at the Asheville Regional Airport and Cincinnati/Northern Kentucky International Airport, becoming the first base at a non-vacation destination.
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 February 2015, Frontier announced that they will begin service to several destinations from Atlanta adding the airport as a focus city. In July, Frontier also began decreasing service from Washington Dulles International Airport removing the airport as a focus city. In early 2016 Frontier announced major route expansion from airports nationwide including Atlanta, Chicago, Cincinnati, Cleveland, Orlando, and Philadelphia. In June 2016, Frontier re-established service to Port Columbus International Airport. In May 2017, the airline announced opening a new crew base in Las Vegas in the fall 2017 to improve operational reliability and potentially create new jobs in Las Vegas. In December 2017, Frontier began service to Buffalo, New York, with service to Denver, Colorado, and Florida, including Miami, Fort Myers, Orlando, and Tampa.
On November 15, 2017 Frontier Airlines announced a $15 billion order for 134 additional A320neo family aircraft. The order, slightly revised under new owner Indigo, consists of 100 A320neo and 34 A321neo. The order also includes the conversion of the remaining A319neo to A320neo. With this order, Frontier Airlines fleet has industry-leading fuel efficiency. The fleet is also one of the most modern and young, particularly in comparison to other low-cost carriers,[nt 1] at an average age of 5 years as of 2018.
As Republic Airways Holdings was in the process of bidding to acquire Frontier in 2009, it was also in the process of acquiring Milwaukee-based Midwest Airlines. Through the fall and winter of 2009, Republic operated its two new acquisitions as separate brands. However, to improve efficiency by better matching aircraft capacity to route demand, Republic began to intermix the fleets of the two airlines, swapping a portion of its higher-capacity planes from Frontier with its smaller-capacity planes from Midwest and vice versa. However, the move caused some confusion amongst the public, as the two brands did not offer the same amenities and did not match the amenities mentioned on the airfare. As a result, in the Spring of 2010, Frontier and Midwest Airlines announced that their brands would merge, with Frontier being the surviving brand. This was a merger of brands only—no Midwest Airlines aircraft was ever operated by Frontier, as by this time, all Midwest Airlines flights were operated on its behalf by other Republic Airways Holdings subsidiaries.
In October 2005, JetBlue's quarterly profit had plunged from US$8.1 million to $2.7 million largely due to rising fuel costs. Operational issues, fuel prices, and low fares, JetBlue's hallmark, were bringing its financial performance down. In addition, with higher costs related to the airline's numerous amenities, JetBlue was becoming less competitive.
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 the approval for 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 nonstop service to Honolulu from Las Vegas.