I was once a passenger in a car when the bonnet flew up and completely blocked our view without warning . I was getting a lift to work with my shift foreman on 2 till 10 and we were doing around 60 mph on a dead straight road near Ellesmere Port. This was in the 60's and the car was a Vauxhall of some type, maybe a Velox. We managed to pull up safely and secure the bonnet before continuing, damage was fairly minimal amazingly, just a crease where it hit the roof. I don't think its much of a problem these days although the Renault Clio I had was subject to a recall to fit a safer bonnet catch.
Pete
I was about to say, a friend of mine had a old Clio and the bonnet flew up on the motorway! He had only been driving for a couple of years at the most. Must have been terifying.