Police confirmed that officers cleared the Frontier plane that landed in Denver on Monday from Seattle, and that “the threat appears to be unfounded at this time.”

Crewmembers found two threatening notes on the plane from Seattle-Tacoma International Airport to Denver International Airport.

A Frontier Airlines flight from Seattle to Denver was evacuated upon landing after reports of what were thought to be threatening notes. Bomb units and police officers were sent to the flight when it landed in Denver, but the notes were later revealed not to be concerning, according to CBS News.