In 1969, a mostly-unknown artist named John Deutschendorf split off from a faltering group he had joined, the Chad Mitchell Trio. He adopted a stage name that paid homage to the Rocky Mountains, a portion of America he treasured, and released a solo album of folk and country songs. A cover of The Beatles' "When I'm Sixty-Four" would initially fare well with consumers due to its familiarity -- but it was hardly the highlight of John Denver's Rhymes and Reasons record. "Leaving On A Jet Plane" was a genre and culture crossing message of pining that struck home for listeners everywhere.
Unfortunately for the singer/songwriter, it wasn't his recording that caught the world's attention. Peter, Paul and Mary (who had earlier helped boost Denver's career through performances of "For Baby (Goes Bobbie)") included a cover of the song on their disc Album 1700 and it would go on to become the trio's only number one hit.
Denver achieved widespread success two years later with 1971's "Take Me Home, Country Roads" and "Sunshine on my Shoulders" but it is "Leaving On A Jet Plane" that is possibly his widest-known (if unattributed) work. The song has been covered by dozens of artists and included on a number of albums. Similarly folky artists like Jewel and Peter, Paul, and Mary have recorded equally mellow versions, while musicians as diverse as punk band Me First and the Gimme Gimmes and Athens-rock Drivin N Cryin have put other twists on the song.
Other performers known to have released a recording of "Leavin' On A Jet Plane":
I can't find enough documentation to prove or disprove it, but I have heard from several people and am willing to believe that this is the most-covered popular music song. Despite the popularity of songs by The Beatles, The Rolling Stones, Led Zeppelin and Elvis Presley, it is still somewhat conceivable.
This song has also been parodied as "Libyan on a Jet Plane" by Sandy Pinkard and Richard Bowden, a comedy songwriting duo. | 
