Cities in Flight is a four-volume series of science fiction stories written by James Blish, originally published between 1950 and 1962, which were first known collectively as the "Okie" novels. The series features entire cities that are able to fly through space using an anti-gravity device, the spindizzy. The stories cover roughly two thousand years, from their very near future to the end of the universe. One story, "Earthman, Come Home" won a Retro Hugo Award in 2004 for Best Novelette. Since 1970, the primary edition has been the omnibus volume first published in paperback by Avon Books. Over the years James Blish made many changes to these stories in response to points raised in letters from readers.