I first heard this song in 1970 or so, on the wonderful, and madly eclectic, WHFS-FM. That led me to buy the album, and that led me into one of the enduring loves, or at least likes, of my life: the English Electric Folky groups of the 60s and 70s.
Light Flight is not electric though, and it's not even all that folky, except for Jacqui McShee's soprano, and John Renbourn's guitar. It's more jazzy than anything else; but there's also Swingle-Singers-style scatting, and dreamy, hippy-dippy lyrics, and a mix of time signatures including 5/8, 7/8 and 6/4. (Or so says Wikipedia; I tried to figure out the time signatures myself, and couldn't.)
Wiki also says, oddly enough, that Light Flight was used as theme music for a 1969-71 BBC drama series, Take Three Girls, about three young ladies sharing a flat in Swinging London.