Preposition use: "in the plane" vs "on the plane"

[AlmostEnglish2]

Hi all,

I was just watching "My Fair Lady" and the scene where she gets told to practise "The rain in Spain stays mainly in the plane" confused me. I am an EFL learner and now teacher and I do understand that we typically say "on the plane" as passengers "on board" a plane, and could say "in the plane" meaning "inside" the plane when emphasising the opposition to "outside" the plane. Why would you say "in the plane" in this context, though?

I do realise this is not a massively important linguistic issue, but these things bug me.

Any help with this will be much appreciated.

 

[probus]

It's not plane, but plain.

 

[Yankee]

Hi all,

I was just watching "My Fair Lady" and the scene where she gets told to practise "The rain in Spain stays mainly in the plane" confused me. I am an EFL learner and now teacher and I do understand that we typically say "on the plane" as passengers "on board" a plane, and could say "in the plane" meaning "inside" the plane when emphasising the opposition to "outside" the plane. Why would you say "in the plane" in this context, though?

I do realise this is not a massively important linguistic issue, but these things bug me.

Any help with this will be much appreciated.

It's "plain" and refers to an area of flat, treeless land.

 

[emsr2d2]

There are a lot of native speakers who also think it's "plane".

 

[jutfrank]

I don't get it. She starts off repeating in the plain and then he says Where does it rain? and she responds on the plain. They then both continue to sing in the plain before his eliciting a second time Where does it rain? before her replying again on the plain.

Here's a clip:

 

[AlmostEnglish2]

Thanks for all your replies!
I never knew it was "plain". I even had this whole explanation in my head that because it doesn't really rain in Spain it's like they only time you would see rain there would be on the way, through a plane window. It does seem ridiculous now... Anyway...
Thank you