August 2, 1919 – Cleveland, Ohio
August 2, 1919 – Chicago, Illinois
Mark Hamilton joined the Air Mail Service on July 4, 1919, but left two months later to finish college. He returned to Texas A&M to finish his degree in chemical engineering. In October of the same year he wrote to Otto Praeger asking for his per diem expenses to be sent along. "I am now a senior in school paying my own expenses. As my finances are getting low, I would appreciate it very much if you would have these accounts rushed as much as possible."
Two years later, Hamilton had finished school and decided that "the Air Mail Service is the most interesting work I can get into." He admitted he hadn't flown for a while, but pointed to his over 100 hours as an Air Mail Service pilot. He noted that he was anxious to get back to flying the mail and even promised to remain in the service for at least one year. His application was not approved.