In 1971 a mysterious man hijacked an airliner in Portland, Oregon, demanding $200,000 and four parachutes. He bailed out somewhere over southwestern Washington and has never been seen again. In today's show we'll tell the story of D.B. Cooper, the only unsolved hijacking in American history. We'll also hear some musical disk drives and puzzle over a bicyclist's narrow escape. Intro: In 1973, Swedish mathematician Per Enflo won a goose for solving a problem posed 37 years earlier. Established in 1945 by a sympathetic actor, the Conrad Cantzen Shoe Fund will reimburse working artists $40 toward a pair of shoes. Sources for our feature on D.B. Cooper: Ralph P. Himmelsbach and Thomas K. Worcester, Norjak: The Investigation of D.B. Cooper, 1986. Kay Melchisedech Olson, The D.B. Cooper Hijacking, 2011. Associated Press, "First D.B. Cooper Clue Discovered," Jan. 18, 1979. Associated Press, "Clue to D.B. Cooper's Fate Found by a Washington Family on Picnic," Feb. 13, 1980. Farida Fawzy, "D.B. Cooper: FBI Closes the Books 45 Years After Skyjacking Mystery," CNN, July 14, 2016. Christine Hauser, "Where Is D.B. Cooper? F.B.I. Ends 45-Year Hunt," New York Times, July 13, 2016. FBI, "D.B. Cooper Hijacking" (retrieved Sept. 18, 2016). FBI, "Update on Investigation of 1971 Hijacking by D.B. Cooper" (retrieved Sept. 18, 2016). David A. Graham and Juleyka Lantigua-Williams, "D.B. Cooper's Final Escape," Atlantic, July 12, 2016. Peter Holley, "The D.B. Cooper Case Has Baffled the FBI for 45 Years. Now It May Never Be Solved," Washington Post, July 12, 2016. Listener mail: Listener Mike Burns sent these photos from the Museum of World War II in Natick, Mass.: A coal torpedo with instructions. Playing cards concealing maps. A baby carriage rigged by the French Resistance to conceal sabotage equipment and a radio. Brian Dewan's song "The Cowboy Outlaw," about Elmer McCurdy. MrSolidSnake745's Musical Floppy Drives on Facebook. Star Wars' "Imperial March" on eight floppy drives. "In the Hall of the Mountain King," from Grieg's Peer Gynt, by Sammy1Am. This week's lateral thinking puzzle was contributed by listener Philip Ogren. You can listen using the player above, download this episode directly, or subscribe on iTunes or Google Play Music or via the RSS feed at http://feedpress.me/futilitycloset. Please consider becoming a patron of Futility Closet -- on our Patreon page you can pledge any amount per episode, and we've set up some rewards to help thank you for your support. You can also make a one-time donation on the Support Us page of the Futility Closet website. Many thanks to Doug Ross for the music in this episode. If you have any questions or comments you can reach us at email@example.com. Thanks for listening!