ARTHUR: How do the wings give it lift?
CAROLYN: What?
ARTHUR: The wings are really heavy. How does bolting two ginormous lumps of metal to a ginormous lump of metal give it lift?
CAROLYN: Oh, because they are wings. They're like birds' wings.
ARTHUR: Yeah, but birds' wings flap. Ours don't flap. They've got flaps, but I once watched the flaps, all the way to Stockholm. And take it from me, they're seriously misnamed. So, so why does having wings make the plane leave the runway?
...
ARTHUR: Oh, yes, about that, um, I wanted to ask you something, Skipper. Mum was telling me this morning the planes fly because they've got wings.
DOUGLAS: Is there anything that woman doesn't know?
ARTHUR: But she didn't really explain, why the wings lift us up.
DOUGLAS: Ah, well, essentially..
MARTIN: Uh, Douglas, he asked me. Listen carefully, Arthur. The wing is curved on top but flat on the bottom. When it meets the air, its split in two. The air that goes over the top has further to go, so it has to go faster to keep up with the air underneath, that reduces pressures above the wing, giving us a lift.
ARTHUR: Ah, fantastic! Thanks, Skipper. I, I totally get it now.
MARTIN: You are welcome.
ARTHUR: Except, why does it have to?
MARTIN: Why does it what what?
ARTHUR: Why does the air on the top have to keep up the air at the bottom? Why don't they just..split up?
DOUGLAS: For the sake of the kids?
...
DOUGLAS: Arthur, you were asking why the air over the wind has to keep up with the air underneath..
ARTHUR: Oh, yes, do you know?
DOUGLAS: Indeed, I do. Attend. The air is not passing over the wing. The wing is passing through the air. So the curved upper side stretches the air forced over it apart, reducing pressure, producing lift. The lift pushes up. The weight pushes down. So as long as the lift is more than the weight, up we go and that, my friend, is how an aeroplane flies.
ARTHUR: Got it! Right. Yes. Cracking. I completely get it now.
DOUGLAS: Good. You see, is that quite easy to grasp when it's explained properly by someone who understands..
ARTHUR: So that's why planes can't fly upside and down?
DOUGLAS: Uh..Yes, they can.
ARTHUR: Can they?
DOUGLAS: Well, of course they can. Haven't you seen the Red Arrows?
ARTHUR: But doesn't that mean the curved side of the wing is on the bottom? So the lift is pushing down as well as the weight. How does that work?
MARTIN: Yes, Douglas. How does that work?
DOUGLAS: Well, Arthur, there's a very simple explanation. But just to finish what we were saying, Martin, I think it's entirely up to you whether you let the cat in the hold freezed to death.