 In February 1966 , just prior to the release of " Eight Miles High " , Gene Clark left the band . His departure was partly due to his fear of flying , which made it impossible for him to keep up with the Byrds ' itinerary , and partly due to his increasing isolation within the band . Clark , who had witnessed a fatal airplane crash as a youth , had a panic attack on a plane bound for New York and as a result , he disembarked and refused to take the flight . In effect , Clark 's exit from the plane represented his exit from the Byrds , with McGuinn telling him , " If you can 't fly , you can 't be a Byrd . " However , it has become known in the years since the incident that there were other stress @-@ related factors at work , as well as resentment within the band that Gene 's songwriting income had made him the wealthiest member of the group . Clark was subsequently signed by Columbia Records as a solo artist and went on to produce a critically acclaimed but commercially unsuccessful body of work . He died on May 24 , 1991 , at the age of 46 , from heart failure brought on by a bleeding stomach ulcer , although years of alcohol abuse and a heavy cigarette habit were also contributing factors . 
