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.
Frontier Airlines was incorporated on February 8, 1994, by a group that included executives of the original incarnation of Frontier Airlines in response to the void left by Continental Airlines' 1993 shutdown of its Denver (Stapleton) hub. Scheduled flights began five months later in July 1994 using Boeing 737-200 jetliners on routes between Denver and four destinations in North Dakota: Bismarck, Minot, Fargo and Grand Forks. By January 1995, Frontier had expanded its route network from Denver and was serving Albuquerque, New Mexico; Billings, Montana; Bismarck, N.D.; Bozeman, Montana; El Paso, Texas; Fargo, N.D.; Great Falls, Montana; Las Vegas, Nevada; Missoula, Montana; Omaha, Nebraska; and Tucson, Arizona with 737's. Like the original airline of the same name, the new Frontier operated a hub at Denver (DEN) and for the first nine years used the slogan "The Spirit of the West" which was displayed above the windows and just behind the cursive letters "Frontier" on the fuselage of their aircraft. In 1999, Frontier signed agreements to begin purchasing and leasing Airbus A318 and A319 jet aircraft and had also added Boeing 737-300 jetliners to its fleet as well. Also by September 1999, the airline was serving destinations from coast to coast in the U.S., having expanded its route network to include Atlanta (ATL); Baltimore (BWI); Bloomington/Normal, Illinois (BMI); Boston (BOS); Chicago (MDW, Midway Airport); Dallas/Fort Worth (DFW); Phoenix (PHX); Los Angeles (LAX); Minneapolis/St. Paul (MSP); New York City (LGA, LaGuardia Airport); Orlando (MCO); Portland, Oregon (PDX); Salt Lake City (SLC); San Diego (SAN); San Francisco (SFO); and Seattle (SEA), all served from its Denver hub.
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. 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.
While its financial performance started showing signs of improvement, in February 2007, jetBlue faced a crisis, when a snowstorm hit the Northeast and Midwest, throwing the airline's operations into chaos. Because jetBlue followed the practice of never cancelling flights, it desisted from calling flights off, even when the ice storm hit and the airline was forced to keep several planes on the ground. Because of this, passengers were kept waiting at the airports for their flights to take off. In some cases, passengers who had already boarded their planes were kept waiting on the apron for several hours and were not allowed to disembark. However, after all this, the airline was eventually forced to cancel most of its flights because of prevailing weather conditions. The fiasco reportedly cost JetBlue $30 million.
After making a codeshare agreement with Lufthansa that went into effect in 2010, jetBlue transitioned to the Sabre reservation system used by Lufthansa, enabling the airlines to sell tickets on each other's flights, transfer luggage and passengers between the two carriers, and combine frequent flyer programs,. By making use of JetBlue's North America routes as a feeder network, the agreement put Lufthansa in a position to operate quasi-hubs in New York–JFK and Boston Logan.