ExpressJet Airlines, which calls itself a “reboot” of the company formerly flying as Delta Connection and United Express, filed for Chapter 11 bankruptcy Monday in Delaware and ceased operations, according to the company website. “We regret that a combination of market and economic conditions lead us to take this action,” the company wrote. Atlanta-based ExpressJet operated over 450 aircraft at its peak. The airline was the world’s biggest operator of Embraer ERJ145 aircraft, a regional jet, as recently as February 2020, but pandemic-induced woes proved a fatal blow for the regional carrier. After acquiring the company from SkyWest Airlines in 2018, United Airlines decided in 2020 to end its flights with the airline amidst pandemic cutbacks. ExpressJet then shut down for around a year before relaunching as Aha!, but the reboot struggled to deal with rising costs and changing travel habits. United finally sold its 49.9% stake in ExpressJet parent company ManaAir in June. Over the past six months, ExpressJet has been flying as low-cost Aha! Airlines out of Reno-Tahoe International Airport to 11 cities across the western United States, as well as ad-hoc charter services. The company pointed to stifled growth, rising costs and lower revenue due to the pandemic as the reasons that led to bankruptcy, according to a press release Tuesday.