The Gremlins has a very good claim to being Roald Dahl's first piece of writing for children. It is certainly one of the first stories he ever wrote. He began work on it in 1942, soon after his first paid piece of writing, Shot Down Over Libya, was published in the Saturday Evening Post. He was working for the British Embassy in Washington DC at the time and sent his finished Gremlins story to his bosses for approval. From there, it was forwarded by British movie producer and entrepreneur Sidney Bernstein on to Walt Disney, who liked the story so much he wanted to turn it into a movie.
The gremlins are little creatures responsible for the various mechanical failures on aeroplanes, as the pilot in the story, Gus, discovers. Taking its inspiration from RAF folklore and the many gremlin tales he had heard during his own time as a pilot, Roald's story went on to tell how Gus tames the gremlins and persuades them to help him return to flying.