Law enforcement and fire officials were investigating a potential threat on a plane at Denver International Airport on Monday afternoon, but police later said the threat was unfounded.Frontier Airlines said crewmembers discovered what they described as "threatening notes" on a plane.

A small fire in the brake system just ahead of the jet’s takeoff prompted the evacuation of 173 passengers and six crew members, the authorities said.

One person was taken to the hospital Saturday afternoon after an equipment problem on an American Airlines flight at Denver International Airport forced passengers and crew to evacuate onto the