I like to be understanding of the situation. I’ll advise them that there is nothing to be afraid of and tell them other comforting things.
Then halfway through the book I’ll read some crash investigation books and it’s all chill…
I would try and tell them what the things are. If they kept freaking out I would ignore them. If it was a long flight I would take sleeping pills and sleep lol. It actually happened once on a 4 hour flight. I had to order two glasses of wine so I wouldn’t notice as much lol
I help them calm down by telling them the sounds, what the flaps do, and how the wheels don’t power the airplane, then, at cruise, proceed to watch Air Crash Investigation episodes on my Ipad whilst telling them about it.
It would depend on how the person would react to some explanations on how planes fly. And I would simply try to meet this person and talk to him/her on all and everything so they can be distracted from the plane noises. It’s always great to meet someone new.
I would lie: Make them more anxious, tell them it’s not the taking-off that is worrisome. It’s the landing. Its the landing gear you have to worry about! :)
„Hey, you’re afraid of flying, aren’t ya? Listen, always look on the bright side of life. At least you won’t die alone.“
But hey, fun aside:
Ask them if they’re ok and offer them to guide them through the flight if they have any questions. Don’t force them though. If the person wants to be on his own, accept it.
And please, don’t start with „flying is actually pretty safe!“. That’s like saying to someone who’s afraid of spiders „They’re actually more afraid of you.“ It won’t help anything.