(Content warning: aeroplanes being destroyed in mid-air, consequent deaths)
Insomnia can lead you to some strange places, and this is one of the places it has brought me recently: an unsolved mystery almost ninety years old, where I humbly propose an explanation of what might have happened.
On 10 October 1933, a Boeing 247 airliner operated by United Air Lines, on the Cleveland to Chicago leg of a journey from Newark, NJ, to Oakland, CA, crashed near Chesterton, Indiana, killing all four passengers and three crew. Subsequent investigation determined that a nitroglycerine charge in the blanket cupboard above the toilet had exploded, blowing the tail off. Two of the four passengers were immediately sucked out of the plane to their deaths; its front end then flipped over, crashed into the ground and burned to a cinder with the other five victims still on board. It is the earliest known case of a civilian plane flight being destroyed by sabotage.
(That is, the first known definite case of sabotage destroying a civilian flight. Just over six months before, on 28 March 1933, a British passenger flight caught fire and crashed in western Belgium, killing all fifteen on board. Suspicions were raised at the time, and have lingered, that one of the passengers might have deliberately caused the crash. But personally, I am not convinced, and I agree with the conclusions of Wout Wynants, who thinks that a bird strike or similar accident severed the fuel lines which then ignited the rest of the plane.)
In 2017 the FBI declassified 324 pages of investigation of the October 1933 crash by its predecessor, the Bureau of Investigation, already run by J. Edgar Hoover. Hoover put his best man in Chicago, the notorious Melvin Purvis, on the case. Before the end of the next year, Purvis would achieve fame as the man who trapped and killed several of Chicago’s most notorious gangsters, including Baby Face Nelson, Pretty Boy Floyd and John Dillinger. The Mob was a prominent element of American life in 1933.
One has to admire the thoroughness of the investigators. Every lead was followed up, with Purvis reporting on the state of play to Hoover personally. But it all led nowhere. Could it have been left-wing activism over a labour dispute? Actually the labour dispute had been resolved a few days before, and anyway none of the crew were involved. What about the package that one of the passengers guarded jealously? It was probably liquor (which was still illegal, for a few more weeks), and his interests did not run beyond baseball and duck hunting. Several travellers had had reservations on the fatal flight and then changed their plans, but all for good and non-suspicious reasons. The case was eventually closed with no resolution.
Three points occurred to me as I read through the files. The first is that no detonating mechanism was ever found. A timing device or pressure switch would have been pulverised by the explosion, but there would still have been some recognisable components in the debris. I suspect that the bomber stowed the nitroglycerine in the blanket cupboard in a glass or metal flask, hoping that it would be spontaneously set off by the shock of an air bump in mid flight, and the fragments of the flask were indistinguishable from the other wreckage. But managing raw nitroglycerine is not an exact science, and also nobody had ever blown up a plane before. So in my view, the Cleveland to Chicago flight on 10 October may not have been the real target of the bomber.
The second point is that although the mechanic who inspected the plane before it took off from Newark said that he did check the blanket cupboard, he admitted that he only slid his hand behind the folded blankets and did not actually take them out to check that there was nothing else there. (Page 65 of the dossier.) I think he missed the fairly small but deadly flask concealed behind them, as did whoever had checked the plane the previous day or days. A fatal mistake; but again, nobody had ever bombed an aeroplane before, so how was he to know?
The third point (see page 228 of the FBI’s 324-page dossier) is that two days before the bombing, on 8 October 1933, the same plane had done the same run from Cleveland to Chicago with two very interesting passengers on board: Joseph B. Keenan (1888-1954) and Adlai Stevenson II (1900-1965). Keenan was an anti-Mob prosecutor from Ohio, who had just been appointed as a special assistant to the U.S. Attorney-General, and three months later became Assistant Attorney General of the Criminal Division. In October 1933, he would have been very high up the list of public officials who were an inconvenience to organised crime. After the war, he was the Chief Prosecutor of the Tokyo War Crimes Tribunal.
Adlai Stevenson II became a notable historical figure. In October 1933, he was in his first government job, special attorney and assistant to the general counsel of the Agricultural Adjustment Administration, but was preparing to become chief attorney for the Federal Alcohol Control Administration as soon as Prohibition was repealed. This would make him interesting to the Mob, but not as much as Keenan. He went on to be Governor of Illinois, was the losing Democratic candidate in the 1952 and 1956 presidential elections (both won by Eisenhower for the Republicans), and was U.S. Ambassador to the United Nations at the time of his death. (His grandfather, Adlai Stevenson I, was elected Vice-President of the United States in 1892 for Grover Cleveland’s second term, and ran again and lost in 1900.)
The investigators actually interviewed Stevenson about the 8 October flight (page 252 of the dossier); he said that he recognised Keenan but did not speak to him until they reached Chicago, and nothing on the flight seemed out of the ordinary.

(The G-Men did not quite dare to interview Keenan himself.)
My theory is that an opportunistic mobster in Cleveland spotted that Keenan was planning to take the flight and somehow slipped the nitroglycerine into the blanket cupboard. Explosives were easy enough to obtain; one would need a little specialised knowledge to pull this off, but only a little – the absence of an actual detonator is telling. And it would be smart of the Mob to have informants in the airports in their areas of operation. I think that the bomber hoped that the explosive would be triggered by an air bump between Cleveland and Chicago, eliminating Keenan and his fellow passengers. (Another possible jolt – someone closing the toilet door too firmly. One of the two passengers who was sucked out had been seated near the front of the plane, suggesting that he was at the rear near the toilet at the time of the explosion.) Indeed, I think it was triggered by an air bump or door slam between Cleveland and Chicago, but two days later than planned, and was not spotted during the cursory checks of the plane in the meantime.
Most of this theory is not actually original to me. The Chicago Tribune ran a story on 3 November 1933 (pages 120 and 136 of the dossier) saying that a gangster brought the nitroglycerine onto the plane on an earlier flight, feared that it would be found if he was searched on landing, and left it in the blanket cupboard. It seems to me vanishingly improbable that anyone would casually take raw nitroglycerine in their cabin baggage in the first place; I think it’s much more likely that it was planted by someone who did not travel on the plane at all (and the investigators did investigate everyone who did travel on it, as far as possible). However it’s close enough to my theory that I think that one of the investigators in Washington had come to much the same conclusions as me, based on the same evidence, and leaked it to the Chicago Tribune. We’ll never know the full story.
These were the seven people who died on United Air Lines Trip 23, the first victims of airborne terrorism:
Pilot: Richard Harold “Hal” Tarrant (“Harold R. Tarrant” in most reports), born 8 April 1908 in Swindon, England; aged 25; married Bessie Olsen in May 1932. Boarded the plane in Cleveland to replace Robert Dawson, later to become a celebrity pilot, who had flown it from Newark.
Co-pilot: Harold Eugene “Harry” Ruby (“A.T. Ruby” in some reports), born 19 September 1905 in Milwaukee; aged 28; married Catherine Davis in 1926; married again to Pearl Eichholz in June 1933; appears to have had a daughter.
Stewardess: Alice Theresa Scribner, born 11 September 1907 in Bancroft, Wisconsin; aged 26; was engaged and planning to get married a few weeks later. Her funeral was conducted by the minister who had planned to preside at her wedding. The first United Air Lines stewardess to die in service.
Warren Fairhill Burris, born 22 July 1888 in Fairhill, Pennsylvania, aged 45 (death certificate says he was 35, but this is wrong). Married Helen Leona Miller in 1918. Radio operator with United who was flying to a work assignment. Two sons and a daughter; the younger son and the daughter both died as recently as 2012.
Emil Smith, born 14 December 1888 in Chicago, aged 44; had sold the family grocery shop and was living on savings; single; attracted attention from the investigators because he brought a package onto the flight which he was very protective of; but in the end turned out to just be an average guy with an interest in baseball and duck-hunting. Although his assigned seat was near the front of the plane, it was he and Burris who were sucked out by the explosion at the back, so he must have been out of his seat at the time.
Frederick Irving Schendorf, born in Wauconda, Illinois on 14 November 1904, aged 28; married Christine Mulroy in 1929; two sons; manager of a refrigerator company. Wrote on a feedback card that he was “quite satisfied with the ride” just before the explosion happened.
Dorothy M. Dwyer, born 13 October 1907 (according to her death certificate), supposedly about to turn 26; her parents were both born in Ireland but emigrated in the mid-1890s; I have not been able to locate her birth certificate, and census returns suggest that she was actually born before 1907 (7 years old in 1910, 17 in 1920; but 24 in 1930); she would not be the first or last person to adjust her official age.
Hers is the saddest story of the lot, and they are all sad stories. Dorothy Dwyer was flying to Reno, Nevada to marry her fiancé, Theodore Baldwin, who had just got his divorce from a previous marriage; she missed the flight she was originally booked on because of a puncture and so ended up on United 23. Baldwin was distraught as he flew east to take her body home to Massachusetts, raving to fellow passengers that his girl had been killed by a bomb; he worked in mining and knew about explosives. Her brother had been killed in a car accident only five months before.
A final point that struck me is that the victims were comparatively young – five in their 20s and two in their 40s. Clearly, commercial plane travel was already reasonably affordable for Americans – Schendorf was well off and flying for business, and Burris presumably had his ticket paid for by United, his employers; but Smith and Dwyer were not especially rich, and were flying for pleasure. (Smith had savings, of course, and Dwyer a rich boyfriend; but still.) It’s for another post, but my sense is that the victims of the Diksmuide crash six months earlier were in general much wealthier.
Thank you for bearing with me.