How the 1913-17 "reform" mayor of New York (defeated in 1917) met his end:
"On the morning of July 6, 1918, when returning from a short military training flight to Gerstner Field, near Lake Charles, Louisiana, his plane suddenly went into a nose dive, causing Mitchel to fall from his plane due to an unfastened seatbelt.[1][9] Mitchel plummeted 500 feet to his death, his body landing in a marsh about a half mile south of the field.[9]"
https://en.wikipedia.org/wiki/John_Purroy_Mitchel
POD: John Purroy Mitchel fastens his seatbelt, doesn't fall out of the single-seat plane, and manages to prevent it from crashing. Any chance that he will later make a political comeback? Maybe in 1933 he, rather than LaGuardia, can win the Republican and Fusionist nominations for Mayor? (There was considerable mistrust of LaGuardia among both Fusionists and Republicans, after all. See
https://groups.google.com/d/msg/soc.history.what-if/qDMQgSws2Ko/f_kR5wwZBukJ for some possible Fusionist alternatives to La Guardia.) Of course, in the general election, he is not going to do nearly as well as La Guardia among the Italians, but presumably there was also an *anti-* Italian vote...
Nevertheless, I'd say the odds are against him. Yes, after Jimmy Walker, New Yorkers wanted an end to blatant corruption, but they didn't really want a reversion to the "scientific" reform of upper-class reformers in the Progressive Era; La Guardia's call for "government with a heart" had more appeal. Still, Mitchel, who was born in 1879, could theoretically be active in New York politics well into the 1940's and even the 1950's. Maybe, even if he can't be mayor again, he can win *statewide* office.