Under the Influence
Denver was clearly an enthusiast, but due to his record for driving under the influence, his piloting license was an issue. Of course, he was not legally permitted to fly. But, despite his record, autopsy reports indicated that he had not been drinking on the day of the crash.
Although he was sober that day, theories were floating around regarding the purpose of the flight. The popular theory is that Denver deliberately crashed the plane. Why? The idea is that he was severely depressed and was looking for the right way to call it a day.