I recall that on one occasion at a rather dignified dinner meeting following a conference in Delft, Holland, my sister, who sat next to him at the table, asked him a question on the mechanics of flight. He started to explain; in the course of it he picked up a paper menu and fashioned a small model airplane, without thinking where he was. It landed on the shirtfront of the French Minister of Education, much to the embarrassment of my sister and others at the banquet.