Many people believe this song is about drugs, but the band claimed it was inspired by a flight where singer Gene Clark asked guitarist Roger McGuinn how high they were in the sky. McGuinn told him six miles, but for the song they changed it to eight.
This story was likely a smokescreen to keep the song in the good graces of sensitive listeners. The band had been doing a lot of drugs at the time, including LSD, which is the likely inspiration. If the band owned up to the drug references, they knew it would get banned by some radio stations, and that's exactly what happened when a radio industry publication reported that the song was about drugs and that stations should be careful about playing it. As soon as one station dropped it, others followed and it quickly sank off the charts.
When we asked McGuinn in 2016
if the song was really about drugs, he replied: "Well, it was done on an airplane ride to England and back. I'm not denying that the Byrds did drugs at that point - we smoked marijuana - but it wasn't really about that."