How are patron saints chosen?

I was stumped by this question. Perhaps one wiser than me knows the answer. What process is a patron saint selected for a particular cause (i.e. St. Joseph of Cupertino, patron of aviators and astronauts)? Who decides, where is it discussed?

This is something that is under the jurisdiction of the Congregation for the Causes of the Saints, a department of the Roman Curia in Rome. The Congregation does the investigation and presents its findings to the pope. The pope is the one who makes official the patronage of a particular cause by a particular saint.

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