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.
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.
In late 2009 Republic began to consolidate administrative positions and moved 140 jobs from the Frontier Airlines Denver headquarters to Indianapolis, Indiana. Shortly after that, in January 2010, Republic Airways announced that it would move all of its executives to Indianapolis. In February the Denver Business Journal stated that the headquarters would be moved "soon". Despite this, according to the Denver Business Journal, Frontier Airlines will still maintain a local headquarters in Denver to house Training, Marketing, Customer Reservations, and Scheduling & Planning teams after extending its lease on the building through 2020.
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 1997, Maverick Airways was operating code share service for Frontier with de Havilland Canada DHC-7 Dash 7 STOL capable turboprops between Denver (DEN) and two destinations in Colorado: Grand Junction (GJT) and Steamboat Springs (SBS). However, the service was short lived as Maverick encountered financial challenges and then ceased all flights.
In 2011, JetBlue made interline agreements with Virgin Atlantic and Jet Airways, both of which have since been terminated. Since 2012, JetBlue has had an interlining agreement with Air China. It also established an interline agreement with Porter Airlines connecting from Billy Bishop Toronto City Airport to US destinations through Boston and Newark.
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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.