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 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.
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At 19″ wide, the middle seats in the airline's Airbus 321s, A320s, and A319s are wider than the window and aisle seats and, as of July 2015 when the airline began installing them, are the widest middle seats of any airline in the U.S. The A321ceo and A321neo, utilized on longer flights, features industry-standard seat pitch of 30"-32". The airline uses a seat pitch of only 28″-29", the tightest seat pitch of any airline in the United States, on their A320ceo and A320neo, typically operated on shorter flights. Frontier Airlines has 28"-31" on the Airbus A319, which they are phasing out. Main cabin seats are "pre-reclined" by the airline and there are no televisions mounted at any of the seats in order to save weight.
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.
As of 2018 it ranked No. 402 financially on the Fortune 500 list of the largest United States corporations by total revenue. JetBlue Airways operates over 1,000 flights daily and serves 102 domestic and international network destinations in the U.S., Mexico, the Caribbean, Central America and South America. JetBlue is not a member of any of the three major airline alliances, but it has codeshare agreements with 21 airlines, including member airlines of oneworld, SkyTeam, Star Alliance, and unaffiliated airlines.
In 2014, Frontier announced it would be transitioning into an ultra-low cost carrier. Frontier will also cut several flights and jobs at their Denver hub and transition them to different markets. On January 16, 2015 Frontier announced that it will close both its Denver and Milwaukee call centers, laying off 1,300 employees and outsourcing the jobs to call center company, Sitel, which operates a large call center for Frontier in Las Cruces, New Mexico. As part of its transition to an ultra-low-cost airline, Frontier Airlines joined Spirit and Allegiant in June 2015 in removing its toll-free telephone number for customer service.
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.
In October 2013, jetBlue introduced Mint, a premium cabin service on transcontinental and select Caribbean flights. The service began in 2014, using the Airbus A321-231 aircraft ordered by jetBlue. These planes are outfitted with winglets, as well as with "lie flat" seats, and moveable partitions that can create small suites on the airplane. Called "Mint" by jetBlue, these planes are configured with 16 business-class seats and 143 economy seats, instead of an all-economy configuration of 190 seats.
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.