Challenge us with a non-famous line from a movie

Braveheart?

You got it. At the end of the defenestration scene.

I could hear it in that tone.

Patrick McGoohan stole that movie so hard he should have gone to prison.

Some more clues:

The movie is based on a French farce and has been remade in different languages around the world.

Thelma Ritter plays the main character’s housekeeper and is sworn to secrecy.

The arrival of the protagonist’s old buddy threatens to upset his elaborate scheme of multiple deception: “One up, one down, and one here.”

The main character’s English fiancee likes to have kidneys for breakfast because “They’re good for the complexion.”

Any more information would result in a complete giveaway if you’ve ever seen the movie.

Okay, one more clue:

The name of the movie shares that of an aviation industry giant.

If this doesn’t give you the answer, I don’t know what will.

Tune in tomorrow and find out!

Boeing, Boeing?

BINGO!

Tony Curtis is concurrently engaged to three gorgeous airline stewardesses (one English, one German, and one French) who are never in town at the same time:

Still in play.

Still in play.

I believe this was The Sound of Music, the latter half spoken by Captain Von Trapp to one of the Nazi flunkies.

“I like to think that you killed someone. It’s the romantic in me.”

Claude Rains as Major Renault to Rick (Humphrey Bogart) in Casablanca

One of many great lines from the movie, and very arguably not “non-famous”. But thanks for quoting it.

“Archelon!”

That’s the trick with “Casablanca” - there are so many good lines and so many people that live the movie (myself included!) that it’s hard to find a line people don’t readily recognize.

Correct.

“For one thing, it gives Givenchy a night off.”

“He has his father’s eyes.”
“I want you to hold it between your knees.”
“I bet you’re gay.”
“You can’t print that!” (in response to a two-word music review stating “Shit Sandwich”.)
“Mr. Rusk, you are not wearing your tie.”

…Spoilered because (extremely!) violently mysogynistic (one of the creepiest all-time scenes I’ve ever seen)

[spoilered] “Ever seen what a bullet does to a woman’s pussy? That you should see.”[/spoilered]

Rosemary’s Baby?

Monty Python and the Holy Grail.