Helicopter Slams Into Mountainside After Sudden Mechanical Failure, Passengers Escape Moments Before Impact Boulder County, CO — A sightseeing helicopter crashed into a steep mountainside Thursday afternoon after what investigators believe was a sudden mechanical failure, sending the aircraft cartwheeling down a rocky slope in a shower of debris. Miraculously, all passengers survived after managing to exit the aircraft just seconds before the final crash. The dramatic video begins with a group o