The first passenger aeroplane lost to a terrorist bomb

A fascinating entry in Wikipedia:

On October 10, 1933, a Boeing 247 propliner operated by United Air Lines and registered as NC13304, crashed near Chesterton, Indiana. The transcontinental flight, carrying three crew and four passengers, had originated in Newark, New Jersey, with its final destination in Oakland, California. It had already landed in Cleveland and was headed to its next stop in Chicago, but exploded en route. All aboard died in the crash, which was proven to have been deliberately caused by an on-board explosive device. ...

Investigators who combed through the debris were confronted with unusual evidence: The toilet and baggage compartment had been smashed into fragments. Shards of metal riddled the inside of the toilet door while the other side was free of the metal fragments. The tail section had been severed just aft of the toilet and was found mostly intact almost a mile away from the main wreckage.

Melvin Purvis, head of the Chicago office of the United States Bureau of Investigation described the damage: "Our investigation convinced me that the tragedy resulted from an explosion somewhere in the region of the baggage compartment in the rear of the plane. Everything in front of the compartment was blown forward, everything behind blown backward, and things at the side outward." He also noted: "The gasoline tanks, instead of being blown out, were crushed in, showing there was no explosion in them."

An investigator from the Porter County coroner's office, Dr. Carl Davis, and experts from the Crime Detection Laboratory at Northwestern University examined evidence from the crash, and concluded that the crash had been due to a bomb, with nitroglycerin as the probable explosive agent.