It is one of the most famous songs from last century. The problem is that we don't have good lyrics for it, partially because this song was never played live. We only have a few versions of it, the most famous of course being the one from Physical Graffiti, which should be our reference I guess.
I will copy the most famous lyrics you can find on Google and point out the troublesome parts of it:
I've been to London, seen seven wonders I know to trip is just to fall
I used to rock it, sometimes I'd roll it
I always knew what it was for
There can be no denying, that the wind'll shake 'em down
And the flat world's flying, and there's a new plague on the land
Traversed the planet, when heaven sent me
I saw the kings who rule them all
Still by the firelight and purple moonlight I hear the rested rivers call
And the wind is crying, from a love that won't grow cold
My lover, she is lying, on the dark side of the globe
You got me rocking when I ought to be a-rolling
Darling, tell me, darling, which way to go
You keep me rocking, baby, then you keep me stolen
Won't you tell me, darling, which way to go, that's right
Oh how I wonder, oh how I worry, and I would dearly like to know
I've all this wonder, of earthly plunder, will it leave us anything to show
And our time is flying, see the candle burning low
Is the new world rising, from the shambles of the old\
The confusion lies in the bold parts of the song.
Some people would say that "and the flat world's flying" really is "and the flat world's dying" which would slightly make more sense, given that it is wildy accepted that this song is about a ship from 1800 but I can clearly hear an "L" sound when Robert Plant sings this line. The problem is that "and the flat world is flying" doesn't really make sense as a sentence.
Another people suggest that "and the flat world is flying" really is "and the flag we're flying" which does sound more fitting to what I listen and makes much more sense as a sentence. In this version the (first) bold line of the lyrics above become:
And the flag we're flying is the new flag of the land.
I would like native english speakers to tell me if this line can be the correct one, because it sounds to me that the word "on" is more fitting than "of" in that line that Plant sings.
About the "Traversed the planet", I searched the pronounciation of "traversed" and it seems impossible for me that Plant sings that word in this music. The alternative phrase for that would be "in fields aplenty", which would sound more correct to me.
link to the alternative lyrics here
EDIT: I've found a website from a guy who made a deep research on ALL of Led Zeppelin's lyrics and all my doubts about this band are solved.