"Not gonna fly."

What does this sentence mean?
And, what kind of situation is this sentence usually used?

Vedi una traduzione

Not gonna fly .....
is a really great idiom.

It means - that’s not going to work.
It can refer to all sorts of things that aren’t going to work, or be ok.



Do you understand what the underlying meaning of this phrase is and where it comes from?

Think about flying -
an airplane has to have everything put together just right FOR IT TO FLY,
FOR IT TO TAKE OFF AND FLY.

If there is a flaw in the design - IT WON’T FLY
It won’t take off.
It will stay on the ground.

Do you see the phrase now?

IT’S NOT GOING TO ( IT’S NOT GONNA) FLY

****
So an employee wants to take off 6 weeks for vacation - that’s not gonna fly with their boss.
Meaning - the boss is not going to ok such a long vacation. That idea isn’t going to work - it won’t take off.

A kid (who lives in the city) wants his family to get him a pet horse for his birthday. That idea isn’t gonna fly. There’s no room for a horse in their apartment.

Tim brings an unusual design idea to his work meeting - a colleague tells him - it’s too expensive
and “ that’s not gonna fly with our budget”


Note - we don’t say the opposite of this idiom - we don’t say “That’s gonna fly!”
I do not know why though.