John Athens was on a Frontier Airlines flight when he saw 'the legs of a human spinning around in the engine' as the jet struck and killed a person

A Frontier flight bound for Los Angeles turned into a real life nightmare after a person was fatally struck during takeoff.

New thermal-imaging surveillance footage has captured the moment a person walks onto a runway at Denver International Airport before being struck and killed by a Frontier Airlines jet. The collision occurred at 11:19 p.m. Friday night as Flight 4345, bound for Los Angeles, was accelerating for takeoff.