jetBlue expanded service to the Caribbean, including to St. Maarten and Puerto Plata commencing January 10, 2008. With these additional destinations, jetBlue serves a total of twelve Caribbean/Atlantic destinations including Aruba; Barbados; Bermuda; Cancún; Nassau; Aguadilla; Ponce; San Juan, Puerto Rico; Santiago; and Santo Domingo, Dominican Republic.[citation needed]
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.[55] In June 2016, Frontier re-established service to Port Columbus International Airport.[56] 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.[57] In December 2017, Frontier began service to Buffalo, New York, with service to Denver, Colorado, and Florida, including Miami, Fort Myers, Orlando, and Tampa.[58]
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.[83] 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;[84] 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.[85] A decision was expected by March 2010,[86] although a move would not happen until 2012, when its lease in the Forest Hills Tower expired.[87]

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.[88][51][89] 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.[90]
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.[82]
In July 2012, the U.S. Department of Transportation fined Travelocity $180,000 after discovering that Travelocity's “flexible dates tool” did not always include fuel surcharges that were part of many international airfares in violation of the Department's rules requiring all carrier-imposed surcharges and fees to be included in every advertised fare. In addition, the DOT found that the customer was informed only on the final page before purchasing the ticket that some itineraries required a paper ticket with a minimum additional delivery fee of $29.95.[29]
The initial JetExpress partnership with Mesa ended in January 2004, when Horizon Air was selected to operate the routes. Horizon utilized slightly larger CRJ-700 regional jet aircraft on these routes. In August 2006, Frontier and Horizon ended their partnership.[64] While Frontier was generally pleased with Horizon's operation, the carrier decided that it needed to revisit the agreement and find a provider with additional regional jets to grow the operation. The last of the CRJ-700's was returned to the Horizon Air fleet on November 30, 2007.
Buffalo to Orlando Buffalo to New York Buffalo to Fort Lauderdale Buffalo to Fort Myers Buffalo to Boston Seattle to New York Chicago to New York Syracuse to Orlando Phoenix to Boston New York to Los Angeles New York to Orlando Los Angeles to New York Houston to New York Orlando to New York New York to Las Vegas Boston to Las Vegas New York to Chicago Burlington to Orlando New York to San Francisco San Francisco to New York
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.[105][106]
In February 2002, the airline launched its first regional product, Frontier JetExpress, initially operated by Mesa Airlines using CRJ-200 regional jets. Similar to "express" operations of other carriers, Frontier JetExpress was targeted for markets to and from Denver that do not generate traffic sufficient to support Frontier's smallest mainline jet, the Airbus A318, but could still offer lucrative business with a smaller jet. 

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.[citation needed]
Advanced Air Air Choice One Air Flamenco Air Sunshine Bering Air Boutique Air Everts Air Frontier Flying Service Gem Air Grand Canyon Airlines Grand Canyon Scenic Airlines Grant Aviation Griffing Flying Service Hageland Aviation Services Island Airways JetSuiteX Kenmore Air Key Lime Air Makani Kai Air Mokulele Airlines New England Airlines Penobscot Island Air Reliant Air Rectrix Aviation San Juan Airlines Scenic Airlines Seaborne Airlines Servant Air Southern Airways Express Star Marianas Air Surf Air Taquan Air Tradewind Aviation Tropic Ocean Airways Ultimate Air Shuttle Utah Airways Vieques Air Link Warbelow's Air Ventures Wright Air Service
jetBlue experienced its first-ever quarterly loss during the fourth quarter of 2005 when the airline lost $42.4 million, enough to make them unprofitable for the entire year of 2005. The loss was the airline's first since going public in 2002. JetBlue also reported a loss in the first quarter of 2006. In addition to that, jetBlue forecasted a loss for 2006, citing high fuel prices, operating inefficiency, and fleet costs. During the first quarter report, CEO David Neeleman, President Dave Barger, and then-CFO John Owen released JetBlue's "Return to Profitability" ("RTP") plan, stating in detail how they would curtail costs and improve revenue to regain profitability. The plan called for $50 million in annual cost cuts and a push to boost revenue by $30 million. jetBlue Airways moved out of the red during the second quarter of 2006, beating Wall Street expectations by announcing a net profit of $14 million. That result was flat when compared to jetBlue's results from the same quarter a year before ($13 million), but it was double Wall Street forecasts of a $7 million profit, Reuters reports. The carrier said cost-cutting and stronger revenue helped it offset higher jet fuel costs. In October 2006, jetBlue announced a net loss of $500,000 for Quarter 3, and a plan to regain that loss by deferring some of their E190 deliveries and by selling 5 of their A320s.[citation needed] 
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