The company had charter contracts with Caesars Entertainment to ferry customers to Caesars casino properties through Reno-Tahoe International Airport, Laughlin/Bullhead International Airport and Tunica Municipal Airport. These contracts ended in December 2012 when Caesars Entertainment signed a new contract with Republic Airways to provide the charter service to Caesars properties in Atlantic City, New Jersey, Tunica, Mississippi and Laughlin, Nevada.
In November 2012, Frontier started low-frequency service between Orlando International Airport and Trenton–Mercer Airport near Trenton, New Jersey, which, at the time, had no commercial service. Frontier later expanded service several times from Trenton, and as of June 2016 services 11 destinations. Frontier currently bases three aircraft in Trenton. Trenton Mercer Airport lies roughly equidistant between Philadelphia International Airport and Newark Liberty International Airport.
In the fall of 2001, Allegiant exited bankruptcy and the case was officially closed in early 2002. In March 2002, Allegiant entered into a long-term contract with Harrah's to provide charter services to its casinos in Laughlin and Reno, Nevada. At the same time, the airline acquired its first McDonnell Douglas MD-80 jetliner. From 2002 through 2004, the airline developed its scheduled-service business model. By 2004, Allegiant was flying from 13 small cities to Las Vegas offering bundled air and hotel packages.
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.
In May 2005, the airline's holding company, Allegiant Travel, completed a private equity placement worth $39.5 million that was funded by the investment firms of ComVest and Irelandia II. In November 2006, Allegiant filed a registration statement with the Securities and Exchange Commission in anticipation of a planned initial public offering of its Common Stock. It raised $94.5 million in equity capital with 5.75 million shares worth $18 each. It began trading on the NASDAQ Stock Market under the ticker symbol "ALGT" in December 2006.
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 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.
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.