Frontier Flight Aborts Takeoff After Deadly Denver Runway Breach A Frontier Airlines flight was forced to abort takeoff at Denver International Airport late Friday, May 8, after the aircraft struck a person who had entered an active runway, officials said. The collision triggered an engine fire and emergency evacuation, leaving multiple passengers injured. The incident involved Frontier Flight 4345, an Airbus A321neo, at approximately 11:19 PM local time.