Took a trip from Heathrow around the bay of Biscay on Concorde with my dad about 20 years ago. It was a very windy day and before we boarded we were allowed to wander round the aircraft to take pictures. Sudden gust of wind and a ULD that was sat along with a few others on the apron tipped up, briefly flew a few yards and then dropped on its top. A few seconds earlier and it would have dropped onto half a dozen passengers.