The great airport mystery

The Great Airport Mystery is the ninth volume in the original The Hardy Boys series of mystery books for children and teens published by Grosset & Dunlap. This book was written for the Stratemeyer Syndicate by Leslie McFarlane in 1930. Between 1959 and 1973 the first 38 volumes of this series were systematically revised as part of a project directed by Edward Strarmeyer's daughter Harriet Adams. The original version of this book was rewritten in 1965 by Tom Mulvey resulting in two different stories with the same title. The original version of this book entered the public domain in the United States in 2026; under current copyright laws, this marks the beginning of the trend of a single Hardy Boys book becoming public domain in the U.S. every year until 2050. (This summary is from Wikipedia.)