A passenger aboard a United Airlines flight from Los Angeles to Boston is praising the flight crew and fellow passengers for stopping a man who allegedly tried to open an emergency exit door and stab a flight attendant in midair. Subscribe to WCVB on YouTube now for more: http://bit.ly/1e8lAMZ Get more Boston news: http://www.wcvb.com Like us: https://www.facebook.com/wcvb5 Follow us: https://twitter.com/WCVB Instagram: https://www.instagram.com/wcvb5/