A United Airlines Boeing 247 is destroyed by sabotage, the first such proven case in the history of commercial aviation.

United Air Lines Flight 23 was a regularly-scheduled flight operated by United Air Lines between Newark, New Jersey, and Oakland, California, with intermediate stops. On October 10, 1933, the Boeing 247 airliner serving the flight—registered as NC13304—exploded and crashed near Chesterton, Indiana, United States, en route from Cleveland to Chicago. It carried three crew and four passengers. All aboard died in the accident, which was caused by an on-board explosive device. Eyewitnesses on the ground reported hearing an explosion shortly after 9 pm and seeing the aircraft in flames at an altitude around 1,000 feet (300 m). A second explosion followed after the aircraft crashed. The accident site was adjacent to a gravel road about 5 miles (8 km) outside of Chesterton, centered in a wooded area on the Jackson Township farm of James Smiley.