Then they cast off: you could see the tug aircraft rising and ﬂying away, the drone of their great engines lessening, whilst round in enormous spirals sail the gliders. The sky seems thick with them. Then you hear the swish as, engineless, they come in to land. First one then another, then half a dozen at a time, and the sky still full of them. How are they all going to get in? They touch down at between seventy and eighty miles an hour. Swish they roar across the ground. How is it that they do not crash into one another?