It was perhaps the worst possible timing.As Spirit Airlines and Frontier Airlines were announcing their blockbuster $6.6 billion merger on Monday morning, the entire Frontier network was grounded due to a technical issue. In fact, no Frontier flights had operated since just before the merger announcement. The Denver-based ultra-low-cost carrier asked the Federal Aviation Administration to impose a nationwide ground stop for its flights.Want more airline-specific news? Sign up for TPG’s free new biweekly Aviation newsletter!Things got going again just after noon ET, when Frontier Flight 2131 from Detroit (DTW) to Las Vegas (LAS) departed nearly four hours late. Other flights began departing soon after.Flight tracking sites painted an disheartening picture for much of the morning for Frontier, showing clusters of the carrier’s flights stacked at airports, waiting to depart, but grounded.(Screenshot courtesy of Flightradar24.com)In a statement sent to TPG at 12:11 p.m. ET, the carrier said the issue was resolved.Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.Earlier today, we experienced a technology issue which led to some flight delays and cancellations. The issue was identified and has been resolved. We are working to restore our flight schedule for the balance of the day. We have aircraft currently taxiing. Should have planes back in the air shortly.So far, Frontier has canceled 109 flights on Monday, or 22% of its schedule. An additional 114 flights, or 23% of its schedule, is facing delays, according to FlightAware.More: More than 1,300 cancellations as airlines try to recover from winter stormsThis is Frontier’s first large operational disruption in recent months. It has largely avoided the fate of merger partner Spirit, as well as American Airlines and Southwest Airlines, which have all faced widespread disruptions at various points. It also was largely unscathed during the COVID omicron variant surge in late December, which brought mass cancelations to United Airlines, Delta Air Lines and others.